If there is, let's say, a person that doesn't know very basic stuff about something very general, like, for instance, if someone confuse Austria and Australia and asks a person from Austria whether he likes kangaroos lol, can one possible say "Did you go to school at all?" to mean that he's silly in such a covert form? Or what would you possibly say in such situation? No, not like that... What are ways English-speaking people have a dig at these silly people.
♪郅嫣♪, did you really just say that lol???
You can say "did you really just ask/say that?"
How about "what rock did you crawl out from under?"
I would let the matter drop, as I did when somebody knowing I was from Rome asked me about life
in Greece.
I was in the U.S.A., and I just thought that I did not have to feel superior for just one mistake.
Obviously I don't know capital cities of many countries around the world.
All in all, if that person has something interesting for you, are you are sharing a
conversation with him, let the matter drop, maybe the same person has some kind of 'cultural addiction', like playing chess or studying Physics which in some way make the person live in a cave.
Human qualities are more relevant than some occasional small or big slip in knowledge, if this
qualities are present.
Your course of action, though, leaves you in a bad place if they actually were asking you if you like kangaroos, regardless of being from Austria. Or if they were joking.
I find myself more often regretting hurrying to assume somebody is wrong than actually being baffled by their (circumscribed) ignorance.
I think the most effective response is "I do like them but sadly I've never been to Australia", maybe recited theatrically for comedic effect. Something less insulting and more matter of fact.
But I would go with Katie's one if they say something racist/sexist, etc.
