Is "Bro-Culture" Inherently Sexist?

A woman sued Google last week, saying that she experienced sexual harassment in Google’s “bro-culture.” I won’t go into what she alleges that she experienced because you can read that for yourself if you like, but it got me thinking about what creates “bro-culture.” Is it just that groups of men, when they’re together, will gravitate towards gang-like behavior? Is it the same with women? I don’t think it’s that simple.

What is bro-culture?