It's not just MMA, many things are different between the sexes, especially physically, and no amount of political correctness will change that. I would look upon a man attempting to bear a child in his belly with disdain too.
As far as why MMA is controversial when kickboxing, wrestling, BJJ are not, it's because of ground striking. None of the other sports allow hitting a grounded opponent, when they have very little mobility to defend themselves, and with much less protecting padding than kickboxing (much smaller gloves)... my wife is comfortable watching kickboxing and boxing, but she cringes when she sees some guy pounded into pulp from the mount, says it's too brutal. I disagree and think it's safe with the ref there to intervene, but I can see why some people would find MMA more brutal than the rest.
Interesting facts about the history of MMA in ancient times though, was a nice read.