Actually MMA is less brutal than boxing. A boxer's heavily taped hand, inserted into heavier padded boxing gloves allows them to punch an opponent as hard as they can without feeling the contact or breaking the hand. In boxing, the taped hands are so heavily taped it feels concrete like. In MMA the hands are taped less and the gloves are less padded, which means the hand is much easier broken if a fighter punches as hard as they can. The "frenzied state" you speak of is usually less violent than you think. When a fighter wildly throws haymakers to finish off an opponent, if you watch closely rarely do those haymakers land squarely on the opponent to do any further damage. Just saying...and yes I'm an MMA fan.
With all due respect, I've seen broken noses, broken feet, broken arms, broken hands, etc. all part of MMA. It may be more, less, or equally violent with respect to boxing, but it's still a violent sport that involves beating another human being. In the case of the person in question, if he turns out to be the perp, his penchant for violent sports will just be another piece of the puzzle.