You missed the whole quote
' I think never hitting anyone should be the rule but if a woman hits then she deserves to be hit.'
This leads back to the idea that level of injury or effort is irrelevant to assessing harm.
Op soon got hit by his gf. That is assault.
This means he is allowed to hit her back.
The difference in physical average between men and women is d8sregsrded, that most men can 'hold off' most women. That in this situation the idea of proportionate self defence is out the window and the man can and should give a good as he gets ie if he was hit (slapped) full force then that is what he is entitled to dish out.
The fact that in general the consequences are quite different is irrelevant. The fact that in law, the assault will be dealt with in an individual basis, is also irrelevant.
The point here is that in the name of equality, if a woman gets drunk and slaps a man (assault) then he can go to town.
I get why people say this. I really do.
The fact is though, in general, men are more violent than women, and bigger and stronger. And so telling men they can and should go full force on a woman who slaps them is, not sure its a good idea. Really this is a warning to women isn't it. Treat men with respect.
I have seen women assaulted by men with little reason, and it's happened to me.
Surely the correct advice is, if a woman assaults you, de-escalate, get to safety, tell bar staff or police etc, same as if a woman is assaulted? Why is the advice different for men (give her what for) 7