I think we see it happening because in web, mostly there are men.
It is obvious there are women also, but now we can see something strange, because in internet , insulting a woman is acceptable by many people.

It is very stupid, but i think that internet is a place where hate is #1 thanks to "anonymous" users.
They think being "anonymous" (actually they are not if someone really wants to track them) gives them right to insult the others.