The analogy used by the OP seems apt in many situations, where the person's feminism doesnt really have much relevance to the issue (as in the case of Zoegate). Since in a lot of the school shootings the shooters just happened to be gamers, it wasnt really relevant. (Though, as others have pointed out, the arguers in the Zoegate thing seem to be talking past each other, so I really dont know what to say about it).
For the more "risqué" aspects, I guess you could compare the statements of Anders Brevick (the Danish mass shooter who claimed to use CoD as "training" for the shooting) with those (hopefully few) fringe feminists who advocate violence/abuse of males as feminism (luckily, I have only seen such statements on tumblr, so I'm not too worried. The actual academic movements are a lot less violent). In the end, it's evil/disturbed INDIVIDUALS (I am trying to avoid "crazy" since it isn't necessarily the case) channellings their evil through the communities they identify with.
(If you ever want to be depressed about humanity, check out the "tumblr in action" reddit, a nice collection of screenshots of marginalized groups threatening (with death, torture, etc.) other members of marginalized groups for not being marginalized in the right way. It's very depressing)
Still, this is general human behavior. We always focus on the more outstanding elements of a group. If we are pro-something, we elevate our paragons and ignore the nutters. If we are anti-something, we shine a light on the nutters and ignore those who are making the world better. The Internet has given the "nutters" a very nice podium to speak from, making them much more easy to find.
Which is why I tend to dissociate from "movements". People get way too emotionally involved and lose perspective, too eager to preserve those movements that they associate with their identity, and too readily ignore the bad. If somebody is awful, I focus on the individual being awful, and not the movement.
As many in this thread have said "Feminists should control their nutters", the same SHOULD be said of gamers. There is a HELL of a lot of all-around assholishness (which the community has become innured to) in the gaming community, and while it is unfair to judge a community on the action of individuals, it nonetheless reflects on ALL gamers negatively. We got our own act to clean up! Shut up an asshole today, and tommorow may be a better day.
Note: SHutting up assholes should not, I REPEAT SHOULD NOT be dealt with on the interwebs. It's simply too easy to ignore. This is something you must do with people you know, in RL.
I once had a player who, in a D&D game I ran, made a bunch of sexual jokes (he was playing an S&M mistres... very bad idea of mine to allow that) which was making a female player very uncomfortable. He was being a jerk, I asked him to stop, and we were able to deal with it. The guy still has some negative view about women in gaming, but I hope can change those a little. I know better than to think I can change his whole worldview, but by targeting his behaviors, and exposing him to more female gamers, it might.