"Feminists would be pissed off by this too."
That's simply untrue. But you're half right, as feminists are pissed off pretty much all of the time, except when men get hurt. Anyone who thinks these two things are untrue has a very big misunderstanding about what feminism is, and has done. Evidence: VAWA, child custody, alimony, child support, abortion rights, slut walks, r@p3 shield laws, draconian workplace environments, taking over and infecting all of academia, utter intolerance to any opposing views, stifling of freedom of speech, and so on. Feminism is not, nor has it ever been, about equality, it's a hate driven ideology that only holds itself out to be a movement of peace and love to get the support of the masses behind it.
"The main reason woman-on-man violence is seen as a joke is the idea that women are weak and men are strong, so the idea of a woman hurting a man is funny because men don't get hurt by women. If you get rid of the sexist stereotypes and think women and men are equal then violence is just as bad whoever its happening to."
Humans have inherent biological sexual dimorphism which cannot and should not be ignored by calling them "equal". Men and women are not equal, anyone who thinks this probably misunderstands the word "equal" or basic human biology. The interpretive social construct of these inherent biological differences based upon immediate environmental necessity creates gender roles. Non-consensual violence is unethical, regardless to whom, by whom, or under what circumstances.