Are you kidding me?
Regardless if there is some mind altering brain function that happens during PMS or not, their body feels like shit. A number of uncomfortable physical things happen to the female body during menstruation, and anyone can get moody when they feel bad.
True, everyone should be mindful of their own behavior, and being awful when feeling sick, injured, or even going through menstruation is still being awful. However women on their cycle should be given a little slack at least, they do feel awful, and some are worse than others.