I don't disagree, but I would note that the extent to which people exhibit role-like behavior is probably also somewhat due to cognitive limitations as well as humans not being strategic. You cannot consider every possible scenario or plan, so if you want to be a good friend, a good cook, or a good philosopher, looking at the way that other friends, cooks, or philosophers behave and copying that is generally a pretty good heuristic. It's often better to follow the accumulated wisdom and only make small improvements on that, rather than to try something drastically different that nobody has tried before but which should work in theory, or which at least should if the bullet-swallowers are correct.

Note that this is compatible with Quirrell maintaining that McGonagall wouldn't be enthused with the idea of resurrecting Hermione even if it was pointed out to her: indiscriminately believing in arguments is dangerous, so it would still make sense for her to reject an outlandish argument that she couldn't properly evaluate, like "let's go resurrect Hermione", even if she did genuinely care about Hermione.