If someone asks me a question, I will answer it if I can. Rhetorical questions I can sometime tell when they are, but only if a person is angry. But then I answer then anyway just in case they aren't, even if they are really stupid.
I guess I really took it to heart when I heard the saying there are no stupid questions just stupid answers, so no matter how stupid to me it is, it might be a genuine enquiry, and if it is it seems wrong not to answer.