[Koahku]

Because GamerGate was brewing to become the new chanology, which would have been a disaster for the whole website.

As for 8chan I guess it's because its address was being spammed constantly on every board and it's also considered advertising.

[Karunamon]

That would be grounds for banning advertisment, not mention. As it stands, at least as of a couple months ago, even using the words "gamergate" or "8chan" earned you a three day automatic global ban.

[lmm]

If the original chanology wasn't a disaster, why would gamergate be one?