It's not reasonable to call this a "brain-numbingly stupid" question. The question is legit for someone who has either not studied or not read about the subject matter, but primarily is aware of it via news reporting and random discussions. It's somewhat fair, though still impolite, to call it ignorant. It's fairest to call a question (or questioner) confused. But ignorance and confusion are things that we can fix: by answering the posed question or providing a source to material that can answer the question.

Best solution? Don't call someone's question ignorant or stupid. Instead, be a decent human being and help alleviate the confusion by answering the question.