I've never quite understood how the "guys shouldn't hit girls" thing is still going strong. To me, it reinforces a "women are weaker than men, and must be protected" stereotype that really should be gone by now. But then again, guys being uber-chivalrous when they're with me has always vaguely annoyed me. I'm female, yes. Doesn't mean I'm going to break if I have to open a door myself.
That doesn't mean I'm saying, "Yes, go out and hit girls!" I don't think anyone should hit girls... and I don't think anyone should hit guys, either. I'm all for non-violence, unless violence is the only choice to defend yourself.