I think the social rule of "never hit a girl" is not only ridiculous, but dangerous as well. Take these two stories:

The first is a man beaten into a coma by 3 women, which I actually think was posted here a while back:

http://www.telegraph.co.uk/news/uknews/crime/11731945/MPs-son-attacked-by-girl-gang-in-Leicester-Square-KFC.html

Notice his friends interviews saying "he was not going to hit a woman"

But why not? Why should HE have to be in coma because those women decided that they get to attack him?

And then this story, currently on the front page: https://www.reddit.com/r/MensRights/comments/4osfna/2_girls_beat_up_a_boy_for_protecting_his_autistic/d4fd8mz?context=3

Notice the mom saying she's "proud" that he didn't retaliate...but why? Would she be proud if he let himself get a serious brain injury that left him permanently disabled?

I just don't get why I'm supposed consider the comfort of my attacker in this scenarios. Why should I care if you're female? If I ever get into a public altercation I know it won't be my fault, so it means someone went out of their way to cause a problem. Say I'm walking home from the pharmacy with medication that's essential for my 89 year old grandfather, or myself, and a woman tries to rob my bag or assault me like in these videos...why should I have to hold back and worry about HER safety? I need that medication and I'm not going to let her have it. I don't care if I'm stronger than her. I don't care if she gets a bruise on her face. It's her problem, not mine. She should have thought of that before going out of her way to cause a problem.

I punched a woman in the face once who came at my with a knife to face. I didn't think "o! she's a woman, I'd better stop this knife in a way that is more comfortable and convenient for her!" I just stopped the attack.

Nobody would ask a large country to refrain from striking back on a small country bombing their towns and civilians. No one blames a larger man for reacting to a smaller aggressive man.