I think it's a common category error. The job of an academic linguist is mostly (as I understand it) to study language as-found, but I've met a few people who t

I think it's a common category error. The job of an academic linguist is mostly (as I understand it) to study language as-found, but I've met a few people who take that to mean "linguists -- the experts on language -- say we shouldn't try to 'correct' differences." It comes in a few flavours. Sometimes an assumption that linguists as people are never prescriptive. Sometimes as an argument for the respectability of established dialect (not to say this conclusion is wrong, only the argument.) There is plenty of (mostly non-professional IME) "normative descriptivism" floating around.