Eliezer thoroughly deconstructed Dumbledore's (And Gandalf's) view of evil in Lord of the Rationality. "If the Enemy thought that all his foes were moved by desire for power alone - he would guess wrongly, over and over, and the Maker of this Ring would see that, he would know that somewhere he had made a mistake!"

Even if somehow Quirrell was stupid enough to not truly understand non-sociopathic motives, he would not make the obvious mistake of revealing this weakness to Harry. Harry thinks that Quirrell can't comprehend good because that's what Quirrell wants him to think.

And H&C didn't even fail because of a miscalculation about Hermione's altruism. It was a rookie mistake to not use a different appearance than you did with Zabini. Even if you still wanted to look dark and mysterious, you wouldn't pick the exact same disguise you used earlier, just in case.

Finally, H&C's dialogue is highly unquirrellish. "I hoped for better from you, Hermione. Surely such a Ravenclaw as you, the most intelligent Ravenclaw to grace Hogwarts in a generation, knows that appearances can be misleading." Those are not the words of a Dark Lord who doesn't care about your opinion and is about to wipe your memory.