Before the 1960's, attitudes about language not seen as important; the behaviorist approach to language study saw language as behavior, not as cognitive or mental activity and anything psychological was denounced as mentalism.
Or, study of attitude (esp. toward non-standard language) was seen as dignifying stereotypes and popularizing `unscientific' ideas about language; best to leave this alone. Pseudo-egalitarianism: ignore it and it'll go away.
Some would still advocate ignoring racist and sexist attitudes, especially the social differences associated with racism and sexism.