Sexist morals if anything. To be fair, niether should hit either, but because of the way today is, people think if a man strikes a woman under ANY circumstances, its wrong and he should be punished, even in self defence.
The worst part is women use this to theri advantage sometime so they'll hit a man, abuse etc and when that man finally snaps, it's instantly "Oh I was struck by a man, you heartless bastard!".
Like women kicking men in the balls. they think it's funny but after a while you've just permanently damaged a mans reproductive organ and in some cases, caused them to become sterile. There's been a few court cases when a teenager girl(s) have kicked a kid so badly in the sack he became fertile at only 15, basically destroying all chances of him having a kid from his own DNA.
Obviously if a woman strikes me im not going to openly let them hit me, I'll put their arm into a lock or something to not hit but stop them. Weapons though, they come at me with a knife... Guess who's about to have THEIR crotch kicked...