I'm familiar with who represents GG but what is a SJW?
From what I can discern, they are people that are against discrimination.
A Social Justice Warrior, or a SJW, is as far as I know a degrading term for activists who fight for political correctness.
According to GamerGate, tolerance, equality and political correctness are tainting the integrity of the video games scene because apparently any game that isn't following their supposed status quo where games are male power fantasies and degrade women and minorities in some way or the other, or even worse, have homosexual characters, are SJW games, and everyone who thinks the games scene is mean to any sort of group is considered a SJW too.
Basically, if you have a critical opinion on any character's depiction, you might be a SJW and are a threat to GamerGate because your opinion might cause developers to censor themselves, since GamerGate totally doesn't believe people might do that on their own accord and instead it's those damn SJWs ruining everything. You are generalized to be a person upset by everything who's single goal in their life is to ruin the fun of everyone else, and are the scapegoat for GamerGate to blame everything "wrong" about today's gaming scene on.
Honestly, I wouldn't be surprised if down the line they got delusional enough to blame broken releases and games as a service releases on SJWs, if they aren't doing that already.