Social justice does not necessarily represent equality, but justice for those oppressed. It offers advantageous positions to those deemed underprivileged compared to those deemed privileged. Of course, who is privileged and who isn't is left up to the interpretation of the individual judging. To some, this might seem to be promoting equality, but to others, it might seem to be promoting a certain form of sycophancy to one's self, or a censoring of the real world in the search of a "safe space". I won't pretend to support contemporary social justice movements and activities, but I also won't blindly demonize its intended effects.
That being said, to act as though MRA or GGers are "vectors of hate" is as terrible as lumping in every feminist that hates men with the feminists that honestly just want gender equality. I might not be a mens rights activist, nor be a Gamergate supporter, but I'm not going to blindly distrust and hate these movements simply because I've heard that they're hate spewers.
I know there's more behind Gamergate than harassment of women (though I find the whole movement has since deteriorated into a self-righteous parody of itself), and I also know that, if you support equality, then Mens Rights Activisim deserves a place in this world to exist, regardless of whether or not you believe Feminism is already working to achieve the same goals as said movement. There will be radicals on every side, but there's no use putting up blinders simply because of them.