Re: EDITED: I'd be interested in your definition of "Trotskyite," since nobody as yet seems to have developed a consistent or sensible one.
The problem is that there is no objective way to distinguish "errors of knowledge" from "deliberate rejection of reality".
Just imagine a learned Catholic and a Protestant scholar arguing. Or a Christian, debating a Jew or a Muslim. Sure, I'm an atheist, and I think all of them are full of shit, but I can't use that subjective judgement and not expect them to be insulted and outraged.
Its also a question of manners and common courtesy. You don't tell someone you disagree with he's wrong, and then insist he's stupid because he won't change his mind.