I was told we should be lucky that such school exists, because in most European countries, the mere existence of such school would be "politically incorrect".

I've gotten the same kind of response up here in Canada, heard at least one account to that effect for Russia (Moscow specifically), and south america / africa can arguably be excused because they should start by having schools in the first place (they kind of do, but not enough and not everyone has access to basic education).

As for the middle-east, well, you're either Taliban or you're a poseur heretical scrub, as far as I can tell. So the only "gifted" education available is to be a distinguished and promising elite of the religious teachings of [Insert locally favored sub-sect or religious curriculum].

Overall, your post very much nails all I've seen, though if I had to conjecture the simplest hypothesis I can to explain this behavior and connotation, it would be that people have this belief that everyone has an equivalent amount and distribution of strengths and weaknesses; There cannot be one human who is physically fit, much more intelligent than normal, good-looking, hard-working, and psychologically stable. If all the observable traits are there, one of the less-observable ones must be broken - "This kid is not normal, stay away from him, he could be dangerous."