The advocate is overly quick to claim a proponent has made a fallacy when in fact they have not.
The question mark is because I think the name needs some work, although it could sound quite condescending, which is a plus. An example is a comment I made at Evolving Thoughts <http://scienceblogs.com/evolvingthoughts/2008/09/fallacies_on_fallacies.php#comment-1118789>:
...something is not a fallacy just because it seems like one. This, I think, is one of the hardest things for people to differentiate. Calling someone an idiot [for example] is only fallacious if that's the basis of your argument. E.g., "The type of home insurance recommended by Andy is wrong because he's an idiot." Andy may indeed be an idiot; however, he might (even if by chance) be recommending a home insurance policy that meets your needs exactly.This is similar to, though not the same as, the Fallacy Fallacy.
Whereas the following is not fallacious even though you are still calling Andy an idiot: "Andy is an idiot because he has recommended you get home insurance that doesn't cover you for a fire, and fire cover is essential in any home insurance policy."
I.e., you are saying Andy is an idiot because his claim is wrong, not his claim is wrong because he is an idiot.
Update Oct 11: How's the Red Flag Faux Pas as the name for this mistake? See comments for elaboration.