I've seen doxxing, threats, and general shitheaded behavior from both the "pro-gg" and "anti-gg"/"SJW" crowds. Boogie being doxxed was discussed in this very thread, and here's an example of a pro-GGer being threatened if you need it-
https://twitter.com/GGfeminist/status/520754494313754624
That said, it doesn't help to respond to the shitty people in your group being pointed out by pulling a No True Scotsman and saying that that person is either a false flag or said shitty behavior was made up.
Just admit that some people on your side are assholes, make it clear that you don't stand by their actions, and do what you can to stop them.
But any group/movement that doesn't have a strong leadership/organizational structure attached to it is inevitably going to have a mix of decent people and complete shitheads.
I don't think it's any more fair to judge everyone who associates with GG by its worst members than it is to do the same to Islam, black people, men, feminists, and so on.
This especially applies when we're talking about anonymous or effectively anonymous people on the internet. I can tab over to TweetDeck right now and tweet "Jews did 9/11 #gamergate #notyourshield #yesallwomen #feminism".
Does that suddenly make GG and feminism anti-semetic truther movements?