If a girl is hot and gives me a boner (including good personality), I'm not going to next her based on where she's from. That's what I mean. A girl who would never date a hot rich Indian guy for that reason is listening to something that was taught to her, maybe not consciously, but through socialization. OP asked what leads to this and that's my answer.I don't think that sexual attraction is the same as racism.
For example, I think that the country of Armenia has the most attractive girls I've ever seen. This doesn't mean that I think that Armenians are superior people.
If I don't think the girls from Bangladesh are very attractive, it doesn't mean I dislike them as people or think they're inferior people in any way.
Also, for instance, if I had the same preferences as you, that doesn't mean I'd choose a fat ugly Armenian over a hot sexy Bangladeshi. Gotta go by the girl standing in front of me.
Like @EyeBRollin said, not much you can do about someone else's interest, it's just how some people are, but personally I don't roll that way. You're right, it doesn't mean that there's dislike or hatred toward others. It's more sort of a soft societal pressure that's instilled. In fact I think people like that are missing out.