Then are they really geeks or just have geek tendencies?
Geekdom is a blood pact that one carries with them wherever they go. There's a lot of "us vs. them" mentality, especially in more introverted circles that feel as though normal society is not for them and they will never fit in.
This hostility is aimed at anyone who, to use their vernacular, is a normie. Someone that, as they see it, has had the luck to be able to fit in to the molds society demanded of them, is not "one of them." This includes men, specifically the "high-status," attractive, promiscuous, and athletic men. As well as normal women, who by the real life random number generator we call chance, are a much greater portion of their gender than men. This is one possible reason it may seem like there is large hostility targeted specifically at women.
Women, using only the frequent amount of stories I've heard, are known for their affinity to want to insert themselves into groups they don't belong in and feel like a great injustice has been done upon them by this. There are certain groups of people that your average woman will never be able to fit in, no matter how much activism she engages in. To tie these two paragraphs together, the largest problems I've seen arise of clashes between geeks and normies, are people who want to "be part" of the group in name, but don't want to be part of the group in lifestyle and essence.
These groups are very welcoming to anyone who shows similarity to their members, but like most groups of people, will not tolerate those who wish to disrupt their bubble and way of being. It's like joining a smoker's support group, but coming in and chain smoking in everyone's faces. Then declaring that the hostility you receive is unwarranted. That it is them who should change their ways, not the malefactor.