When we see pejorative terms applied to usages that the writer disfavors, while favored usages are given praise, the label “prescriptivist” seems to fit nicely:
I’ve mentioned before that linguists who defend sloppy colloquialisms and other misuses of the English language invariably do so in impeccable language. As someone pointed out, otherwise they’d have no credibility. If, for instance, you want to defend the use of “ain’t”, you had better do it from a reasoned and learned academic perspective; you won’t get anywhere claiming that “there ain’t nuthin’ wrong with sayin’ ‘ain’t’”.
The word “prescriptivist” fits this kind of post perfectly.