"Nasty, but not sexism. It can happen among girls too, taunting each other for seeming unfeminine by calling them a boy's name - just not as much, because girls aren't as vulnerable to that kind of attack."
I completely disagree. The reason why a girl being called a boy's name not having the same weight behind it is precisely due to the devaluing of femininity. It has nothing to do with girls not being vulnerable to that kind of attack; I find that whole argument extremely comical. If a girl is seen as having masculine traits, that's not seen as bad as a boy with feminine traits because femininity = lesser than masculinity.
http://www.behindthename.com/pnl/72895
"It is human nature to think wisely and act in an absurd fashion." ~ Anatole France