It already is:
http://guides.macrumors.com/Help:Rules_for_Appropriate_Debate
And since name-calling is insulting, it's also a bannable offense:
https://macrumors.zendesk.com/hc/en-us
Playing devil's advocate, simply because I can...
How does one determine if calling someone a "fanboy" is name-calling, or simply applying a factual title to someone, in the same way that you or I would call Obama the president?