I think it's wrong for a guy to hit a girl... but if a girl hits a guy... gender doesn't count.

Now... if a guy hits a girl first, it depends on if the girl is capable of defending herself. I mean if she's a black belt... it's fair right?

But, if a guy (since they are normally stronger) hit a girl whom I knew was incapable of defending themselves, I'd figure it's wrong. This also goes for guys incapable of defending themselves vs. a girl who knows how to fight.