Linguists call this general pattern "standard language ideology." It's the idea that somewhere out there, there's a perfect, unadulterated version of English, and what your everyday person speaks is a poor copy. I call it the kilogram model of language, because there is literally a physical object in France by which the unit kilogram is defined, and there are in fact multiple and worryingly imperfect copies of it around the world. But what linguists have discovered is that language is definitely not like the kilogram. The only place where English really exists is in the minds of its everyday speakers. To the extent that varies geographically and socially, so does English. There are no imperfect copies.