It amuses me that people think that a man shouldn't hit a woman because it'd hurt more than if a woman hit a man. The pain factor here is irrelevant, it's the principle of being able to talk things out instead of physically lashing out at each other that should be prioritised.
I'm not going to hit a woman if she hurts my feelings because it's a ridiculous and emotional knee-jerk action to take, but if she hit me twice (everyone gets a free one) with any intent of causing me pain then I'd hit her back. No doubt she'd have a shocked look on her face and be incredulous at my actions, but what do you expect? For me to roll over and accept physical violence from someone simply because they have a vagina? How absurd.
If it's not ok for a man to hit a woman for no reason then it's not ok for a woman to hit a man for no reason, the force of the punch doesn't even factor into it. And yet somehow there are some women out there who freely admit to being a bit slap-happy sometimes but I bet they'd run to the nearest judge if their partner even threatened to retaliate, and that is a horrible double-standard that needs to be wiped out.