I am going to give my opinion on this matter and you can take it however you like. I believe that one of the reason geek culture has this resentment towards women who identify themselves as geeks is because to them they feel like the opposite sex is only calling themselves geeks now because it is more accepted in today's world. As it is portrayed in pop culture a lot, many geeks were always chosen second when it came to romantic affection from girls who preferred to date the popular jocks. To some geek who are now seeing beautiful girls identifying themselves as geeks, they feel like they are not being legit, and resent them for it. This happens to many different groups of people who have a history of being outcasts or discriminated against. They resentful for how they were treated and sometimes take it out on those who they feel deserve it. Of course that is no excuse for sexism and they are wrong to discriminate against people like that, but the fact is human beings have a huge tendency to hate on those who they feel resentment for.

to answer the question of how to tell a real geek from a faker. For me as a comic book geek, I find it easy to tell whose a faker and who is a proper comic book lover. If a so called comic book geek says DC sucks except for Batman then they probably have never read any of the comics or have not read enough to know what they are talking about, they just watched the movies. Most proper comic geeks like all the comic book companies or at least give a proper or valid reason for liking one over the other. I can't really say anything for other forms of geekdom since I am mostly a comic book geek, but from what I can tell, knowledge and how much you watch, read or play determines if you're a real geek. I hope this helped answer your questions, and I would like to say to all women who call themselves geeks, do not let these jerks get you down because there are rude people everywhere and there always will be, especially on the internet.