GamerGate is very probably a hate group, with no other legitimate purpose. they're known to send people into forums like this to argue politely and coherently that the "movement" is 100% legitimate. typically the person who comes onto a site like this, to argue in that manner, also makes virtiolic sexist and racist claims elsewhere, typically 8chan (previously 4chan - yes, these people are so fucked up that even 4chan banned them).
the specifics of the GamerGate swindle are very, very interesting for understanding how social media works, and can be misused.
http://jezebel.com/gamergate-trolls-arent-ethics-crusaders-t...
TLDR: Rick Falkvinge's book SwarmWise, plus a great deal of sophisticated and very malicious social engineering.