You know, I’m reading a lot of claims that this or that person is crazy these days. People who make that claim might want to reflect on the poor pedigree that such claims, leveled at political opponents, have.
The “reductio ad Hitlerum“, the attempt to refute an opponent’s view by attributing your opponent’s views to the Nazis, is probably one of the most commonly deployed fallacies in blogospheric comment threads and have leached into opinion pieces more generally. It seems to me that a reductio ad Stalinem, an attempt at discrediting your opponent’s views by pointing out that Stalin believed the same thing, is an as-yet inadequately exploited source of new fallacies.
It’s a lot easier to think of those with whom you disagree as crazy, evil, Nazis, racist or whatever than it is to assume they’re as well-intentioned as you, presumably, are and just make different assumptionsm are aware of different facts, or draw different conclusions than you do.