Keep in mind, that it's simply a combination of various martial arts/combat sports. Arms get broken/dislocated in judo. Noses get shattered in karate and kickboxing. Nasty cuts open in boxing.
Ask any kid who plays football why he likes to play football. It will be the same response over and over: "Because I get to hit people." Thus, why it's hard for me to swallow alleged football fans talking about all the brutal violence of some other sport. The long-term health damage done to football players head to toe dwarfs anything in MMA.
The screenwriter and filmmaker John Milius conceived the UFC, originally. He came up with the Octagon cage. He even wanted water surrounding the cage with gators in it. He got the cage, not the moat. If you know anything about Milius, he's all about men and the heroic. He gets it. He always got it. We idolize guys who will stick their noses and fists out, tuck their chins, and rumble, with no one to support them. Less than a minute into the very first UFC fight in 1993, the victorious fighter kicked out the front tooth of his opponent and the tooth flew out of the ring and into the lap of commentator Kathy Long, a kickboxing great. Back in the locker room, competitor Ken Shamrock said that the room went silent and every guy realized that it just got real, and that's what they would face. Guys tend to like that kind of stuff, regardless if some don't want to admit that. They may just rationalize it and accept it in a more respectable sport like football.
BTW, the guy that kicked out his opponent's tooth was involved in a tournament two years later where he, at 210 pounds, fought a 140 Japanese fighter in the first round. The Japanese fighter wrapped up his leg as the fighter stood over him repeatedly eye gouging the little Japanese guy as the incompetent ref stood by clueless. The Japanese fighter persisted and locked up a kneebar, winning the match. His eye was horrible. As he left the ring and entered the hallway to the locker room, his eye swollen shut, he shouted, "I'm coming for you Rickson! I'm coming for you Rickson!" Rickson Gracie, the overwhelming favorite in the tournament, greatest of the famed Gracie Family, god of jiu-jitsu, was his next opponent. The Japanese fighter, Yuki Nakai, was simply outclassed, but fought until he was choked out. Afterwards, they had to remove his eye. I've never read of Nakai saying anything bad about the fighter who ground out his eye or express any bitterness. That is the kind of guy Milius was thinking about when he envisioned the whole spectacle.