I don’t know how you teach our nation’s [US] history honestly without mentioning these facts [slavery] — but in the eyes of a substantial number of voters, teaching uncomfortable facts is indeed a form of liberal propaganda. And once that’s your mind-set, you see left-wing indoctrination happening everywhere, not just in history and the social sciences. If a biology class explains the theory of evolution, and why almost all scientists accept it — or, for that matter, the theory of how vaccines work — well, that’s liberal propaganda. If a physics class explains how greenhouse gas emissions can change the climate — well, that’s more liberal propaganda.