While combat sports are among the oldest out there, modern mixed martial arts are new in the world of mainstream competition. Actually, depending on who you talk to, there may be nothing mainstream about it, as plenty of people of all ages are still terrified of the thought of two tough, trained, musclebound people entering a ring or octagon to wail on each other.

It's one of the purest forms of competition out there and as such, with our softened, frightened, non-violent, helicopter-parent, touchy-feely society, the sport of MMA itself is somewhat of a controversy for some of the products of left-wing community colleges. But it really shouldn't be. There are refs, plenty of regulation, and all those participating are consenting, aware adults who have trained for years.

Even back in the early years of the UFC, there was little if any reason to object to a no holds barred battle between two hulking morons. Nobody was forced into the ring and no spectators had guns held to the back of their heads. It was an entertainment event featuring willing adults, watched and enjoyed by the same.

But alas, even if we enjoy MMA in its current and/or past form, there are plenty of controversies within the sport that have made the last couple of decades of competition even more interesting to watch. Here is our list of the top 15 controversies in the history of mixed martial arts.

15 15. Testosterone Replacement Therapy Ban 

Testosterone replacement therapy (TRT) is exactly what it sounds like. It is literally a medical treatment program through which athletes and non-athletes can control and maintain a certain level of the hormone testosterone. Testosterone contributes to sexual function, bone and muscle health, and mental well being.

Some athletes have abused this system and as such it was deemed to be a performance enhancing treatment and subsequently banned by the Nevada State Athletic Commission. The controversy arose when fighters such as Dan Henderson, Chael Sonnen, Vitor Belfort, and Frank Mir argued that while some bad apples may abuse TRT, they use it to maintain mental stability and happiness in their every day life. Dana White didn't care and the NSAC didn't care so for those who use it as medicine, too bad, so sad.

14 14. Cancelled Events 

This is not limited to the UFC by any means, as two of the final three Strikeforce events were cancelled and ONE Championship cancelled an event a month ago (there are more examples from other promotions too), but UFC 151 and 176 are notorious for having been cancelled.

UFC 176 would originally have seen Featherweight champion Jose Aldo take on Chad Mendes in a rematch of a fight Aldo easily won in early 2012. Aldo sustained an injury, forcing him to pull out of the fight a month early and due to the remainder of the card being weak, the event was cancelled. This was universally disappointing for UFC fans, but didn't cause anywhere near the backlash of UFC 151.

Originally set for September 1st, 2012, the event would feature Jon Jones and Dan Henderson. Hendo took a knee injury a week prior and Jon Jones refused to accept a fight against Chael Sonnen, who had said he would step in despite the short notice. Dana White was unable to find another choice and ultimately, he blamed Jon Jones for "killing the event," and Jones blamed him right back.

13 13. Ridiculous Decisions 

I could have done an entire article on controversial decisions in MMA, but that's been done. Michael Bisping's win over Matt Hamill back in 2007 is one of the most notorious examples. More recently, Georges St-Pierre got his face ripped apart by Johny Hendricks in November 2013, but still won the fight. GSP looked like he got mauled by a bear with a sledgehammer, while Hendricks looked like he had been lightly hit by a preteen with a wiffle bat. With that scrap in mind, there is an unwritten rule in MMA that in a title fight, the reigning champ needs to be knocked out, submitted or beaten so badly that he or she cannot stand, in order for the belt to change hands. This is a source of controversy in many title fights, including Alexander Gustaffson against Jon Jones a couple of years ago.

The list of questionable decisions goes on and on and can be compiled for any MMA promotion, but it is a reality in any competition that involves judges. They are a necessary level of human error for combat sports.

12 12. Christy Mack/War Machine 

This is not the first time an adult film star has been involved with a fighter. Tito Ortiz and Jenna Jameson were the first and had a predictably rocky relationship. It was nothing, however, compared to that of Christy Mack and Jon Koppenhaver (War Machine).

After a confrontation with Mack and one of her male friends, War Machine beat her. He didn't take a few swings and then walk away however, like some dirtbags might do. He punched and kicked her to a point of being near death. She looked like a different person when all was said and done. He was captured a few days later, hunkered down in a motel.

For some time, this incident was considered to be due to the violent nature of MMA itself, but as many fans know, the vast majority of professional fighters are decent people whose skills are for protection and competition only, and would never launch an unprovoked attack. Many in the business also acknowledged that as athletes go, War Machine was among the most thoroughly screwed up and volatile out there.

11 11. Pride FC: Mob Front 

The former Japanese fighting promotion Pride was sold to Zuffa (UFC's parent company) back in 2007, but prior to that it had significant connection to the Japanese mafia organization the Yakuza. One of the key figures who brought this mob involvement in the promotion to the media's attention was Miro Mijatovic, a former manager for both Fedor Emelianenko and Mirko Cro Cop (Filipovic). Mijatovic launched a lawsuit that essentially brought to light many of the misdeeds carried out by the promotion's higher ups and would end in the cancellation of a television contract necessary to the promotion.

10 10. Strikeforce: Nashville Post-Fight Brawl 

One of the most basic rules of sportsmanship is that while you can let emotions run high during competition, bring it down when it's over and be gentlemanly. It's a simple rule but not always followed in practicality. 2010's brawl that followed the main event between Jake Shields and Dan Henderson ranks among the least sportsmanlike events in the history of MMA. Shields won, and during his interview, fellow Middleweight Jason Miller, who had fought earlier in the night, entered the cage and interrupted the conversation.

Shields, Henderson, both of their corner teams, Gilbert Melendez, the Diaz brothers (Nate and Nick), venue security and the referees ended up in a free-for-all melee that looked like something out of WWE.

9 9. GSP and the Vaseline Allegations

I refuse to call this controversy "Grease-gate" because adding "gate" to the end of scandals is an insult to the Watergate scandal. In that controversial event, members of President Richard Nixon's administration broke into the Democratic National Convention at the Watergate Hotel. He denied it, was implicated in the cover up and ultimately RESIGNED FROM THE PRESIDENCY. This is a major event, while deflating footballs or greasing oneself up before a fight are nowhere near comparable. Read a history book, folks.

During Georges St-Pierre's title fight against B.J. Penn in 2009 at UFC 94, while in the corner between rounds, Phil Nurse applied petroleum jelly to GSP's shoulders as well as his face. While it's fine for cuts and on the face, it is illegal on other parts of the body. Grappling is easier when an opponent cannot grip you.

An investigation took place and while the NSAC did not indicate that St-Pierre and his camp were completely innocent, no serious disciplinary actions were ever taken. All parties involved stated that they had done nothing wrong and while many fans still cite this as a reason for disliking the now-semi-retired Welterweight king, he and his camp have said the entire issue is a misunderstanding.

8 8. Fighters Not Releasing Submission Holds 

I'll never claim to be the perfect example of polite and admirable behavior but there are some rules of etiquette and manners that are pretty easy to follow. "Stop wrenching the limb when your opponent taps" is one of them. Frank Mir has broken the arms of two opponents. Tim Sylvia with an armbar back in 2004 (which was legit, as Sylvia wanted to keep going) and again against Rodrigo "Big Nog" Nogueira, who also refused to tap. He's been accused of holding submissions too long, but both of the maniacs he injured refused to tap; it's their fault.

Rousimar Palhares is the most significant offenders in the group of grapplers who crank holds too long. Don't get me wrong, he's skilled and it's damn impressive that he can lock in these submissions, but there are too many examples of refs having to crowbar him off of an opponent who has already tapped. Tomasz Drwal was the first significant instance and in 2013 it was his heel hook against Mike Pierce (who tapped seven or eight times) that got him banned from the UFC.

Renato Sobral notoriously held a chokehold at UFC 74 that put David Heath to sleep. He then admitted to that being his intention and was fined $25,000 and lost his contract with the UFC.

There are more examples, but you get the idea.

7 7. Dana White - The Man, The Myth, The Mouthpiece 

I've said it before and I'll say it again, Dana White is among the best trash talkers in MMA. Whether you are a journalist, a fighter, an analyst or a rival promotion, he has something unpleasant to say about you. Dana White has enraged feminists, the gay community and of course the legions of fighters who he has called all manner of unkind things.

Two of his most recent comments include mocking wrestling by calling it fake (it is, stop dwelling on it) and criticizing fighters who thank Jesus after fights. When you compare him to the heads of other sports leagues such as Gary Bettman and Roger Goodell, you realize that he adds to the entertainment value of his sport.

6 6. Frank Mir Wanted to Kill Brock Lesnar 

MMA has some prolific trash talkers. Conor McGregor is probably the best right now, having told Chad Mendes he was so fast he could "rest my b**** on your forehead." In the past Tito Ortiz and Ken Shamrock had some solid back and forth smack talk way back in the UFC's early days, and Michael Bisping, Josh Koscheck and Chael Sonnen also have reputations for being quick-witted fighters who can back it up in the Octagon.

Frank Mir took it to another level and a very unsportsmanlike one, when he said "I want to fight Lesnar. I hate who he is as a person. I want to break his neck in the ring. I want him to be the first person that dies due to Octagon-related injuries." It is one thing to talk about breaking someone's arm or breaking a nose, but Mir caught a great deal of bad press for expressing his desire to murder an opponent.

5 5. Pot Suspensions 

One of the finest stand-up comedians of all time, Robin Williams, said it best when arguing that there is no way marijuana is a performance enhancing drug. He was refering to snowboarder Ross Rebagliati, who lost his gold medal due to having pot in his system during the Nagano Olympics. "The only way weed is a performance enhancing drug is if there is a giant Hershey bar at the end of the slope."

Plenty of mixed martial artists have been suspended from the UFC due to testing positive for substances. Plenty of these punishments are legitimate but there is tons of backlash with regard to pot being on the banned substances list. Former Strikeforce and WEC champ Nick Diaz is the most recent and one of the biggest names to have been suspended for texting positive for the drug.

4 4. UFC's Reebok Deal 

Earlier in 2015, the UFC signed a new sponsorship with sports apparel company Reebok. Calling this deal "poorly received" would be like calling World War II "a little skirmish." Plenty of fighters have spoken out against it, as they receive significantly less under the new sponsorship protocols. Joe Rogan has indicated that it isn't good for the fighters or for Reebok, as the company has received negative press as a result and one of the best cutmen in the business, Jacob "Stitch" Duran, was fired from the UFC for speaking out against the deal. Since the ink has dried, there has been more talk of fighters unionizing and many consider it to be clear now that the promotion treats its fighters poorly.

3 3. Fallon Fox 

"That is a lying, sick, sociopathic, disgusting freak. And I mean that. Because you lied on your license to beat up women. That's disgusting. You should be embarrassed yourself. And the fact that Florida licensed him because California licensed him or whoever the hell did it, it's an embarrassment to us as fighters, as a sport, and we all should protest that. The woman that's fighting him, props to you. I hope you beat his ass, and I hope he gets blackballed and never fights again, because that's disgusting and I'm appalled by that."

That was Matt "Meathead" Mitrione, living up to his nickname. He said what some people were thinking, but what could have been said much more diplomatically. His words were in response to the news that mixed martial artists Fallon Fox, who competes as a woman, was born a man. This sparked a conversation in the world of combat sports over which sex transgender athletes should compete with.

Doctors and league officials seem torn to this day over whether a transgender woman still has a "manly" enough build to compete in a fair fight with women. Ronda Rousey was asked about a potential fight with Fox and stated that she would be fine with it, but noted that she still considers Fox to have advantages due to bone density and male bone structure.

2 2. Gilbert Yvel: Referee KO  

It doesn't matter what sport you're playing, whether hockey, football, baseball, tennis, MMA, you cannot hit the ref, umpire, or whatever you want to call him/her. It doesn't matter how much of a slack-jawed moron he or she is and it doesn't matter if they have been paid off. If you hit a ref, you immediately become the bad guy. Between 1998 and 2004, Yvel was disqualified three times. Once for biting, his second was for eye gouging. His third and final, when he knocked out the ref, was due to the ref repeatedly stopping the fight and disagreement between the two about how to resume. For a few years after this event, Yvel had some problems getting licensed to fight in Nevada.

1 1. "Human Cockfighting"  

This is an interesting controversy because it is the first for the UFC. It nearly saw the sport banned altogether, but ultimately the scandal and brutality of the contest was what helped it earn so much media presence early on. In the early and mid 1990s, the UFC was a spectacle, advertised as the type of event in which two men would enter a cage and only one would exit. People ate it up! How could they not? At the end of the day, we're all a little sick and just want to see someone in pain.

Senator John McCain and many others, however, did everything they could to get it banned, saying it was barbaric and just a form of human cockfighting. Thus the UFC received all the free press it would need to continue to grow in viewership. Ultimately, the promotion turned from being a disturbing spectacle to a legitimate combat sports promotion and even Senator McCain, who was a boxer during his time in the U.S. Navy, has hinted that he actually likes the sport, as long as it is regulated.

Dana White and others within the organization have called John McCain the best advertiser they have ever known.