I do agree that the no vetting is a problem. It's a problem with Twitter in a general sense though, not Gamergate specifically, which is why I mostly use Reddit's KotakuInAction board for my Gamergate interactions and basically ignore Twitter. I consider Twitter to be cancer.
And it seems to me that you want to judge the entire thing based on a minority of bad apples simply because you disagree with them ideologically. Think carefully if this is the standard you want to set. Because if that's where we're going, then I'm going to be able to claim that feminism is about man-hating because there are a handful of feminists that use the #killallmen. I'm going to be able to claim that BlackLivesMatter is about harassment because of those people that were interrupting Bernie Sanders. I'm going to be able to claim that Islam is all about terror and violence because of ISIS. Consider carefully just how much hypocrisy you're willing to indulge in when you want to say that those groups can't be defined by their worst elements but this one can.
If this guy gets to represent Gamergate because he used the hashtag, he also gets to represent Australian leftists since he posed as one of them as well. Do we have any Australians on this board? I'd love to see how they can possibly defend themselves for their affiliation with this clown!