Compared to boxing it is less regulated, although it has tightened up significantly from its earlier days.
Martial arts as commonly practiced are basically sports, rarified to certain, limited moves. Obviously so: there's stuff athletes can't do that a fighter would in a real fight, because sports can't afford to have their athletes seriously injured (potentially permanently). The attraction of MMA is that it more represents a real fight, because in real life, your opponent is going to try anything that works, not restrict themselves to inefficiencies like fists / grappling only.
However, the nature of being closer to a real fight therefore makes it more visceral - unpleasant for people who don't like fighting, and attractive to those who do. There is a certain segment of the populace that particularly valorises strength, fighting, discipline, and that's often the far right. As MMA heavily appeals to them and forms part of their recruitment, so MMA will reflect them in return as they are a substantial proportion of the audience and competitors.
I used to watch boxing. As I got older, the more I became ambivalent, given the nature of two people inflicting pain and damage on each other. I'd still say boxing or MMA is well within the bounds (as a well regulated sport) of what people should be allowed to do with themselves and others as consenting adults. It also potentially provides a useful outlet for aggression within safe limits. But nor can I avoid the feeling that there can often be something distinctly unhealthy in atmosphere around some martial arts, too.
