[msla]

One of the worst aspects of "conversational racism", the kind of racism which manifests itself in talking about attitudes and expression of opinions, is "but they're one of the good ones": "Oh, I don't like members of group Y, they're all crooks, but I like that person. They're one of the good ones."

It's so bad because it makes it impossible to refute blanket assertions by pointing to specific examples. The usual understanding of "the exception that proves the rule" (not any of the sensical interpretations of that saying, but the usual understanding of it) is a broader example of this: I have a blanket assertion, you disprove it by pointing to a contradictory example, and my belief in that blanket assertion gets stronger, as opposed to weaker, due to that thought-terminating cliche.