Roland, a loyal MR reader, sends me this quotation from Max Weber:
The primary task of a useful teacher is to teach his students to recognize 'inconvenient' facts - I mean facts that are inconvenient for their party opinions. And for every party opinion there are facts that are extremely inconvenient, for my own opinion no less than for others. I believe the teacher accomplishes more than a mere intellectual task if he compels his audience to accustom itself to the existence of such facts. I would be so immodest as even to apply the expression 'moral achievement', though perhaps that may sound too grandiose for something that should go without saying.