Understandable reaction, but I think it's good to remember that most people are going to have fuzzy understandings of these things and will naturally ask somewhat naïve questions like this. Personally I think it's better to find ways not to be too hard (or hostile) when responding with better information, else they get the swift idea 'well, if they're going to treat me like an arse then me mind's made up,' and all that jazz. And nothing changes.
Just my tuppence of course.
My original comment / response appears at the top of the thread, so feel free to critique, TBF.