If you believe that calling someone a racist basically means "there is no argument against what was said" then you obviously agree that it's a troll post. Why would you allow it? And, by allowing it, you must know things will never change. Sure, Ignore and move on - I get it, but would't it make more sense to put the onus on the troll rather than the recipient?
If A person has no other argument (as you agree) than to lash out and call someone a racist, it is them who should be accountable. Instead of telling us to "just move along", how about telling them that if all they got is shouting racist - don't bother posting? Wouldn't it make more sense to stop the action that is causing the problems?
You still seem to want to allow the agitator to roam free, while you punish the retaliation. Must be a Brad Marchand fan.
Seems pretty simple to me; Call, imply, suggest, infer that a poster is racist (even thinly veiled racist insults that MH seems to approve of) and you get an infraction.