The UN's definition of racial descrimination:
"the term "racial discrimination" shall mean any distinction, exclusion, restriction, or preference based on race, colour, descent, or national or ethnic origin that has the purpose or effect of nullifying or impairing the recognition, enjoyment or exercise, on an equal footing, of human rights and fundamental freedoms in the political, economic, social, cultural or any other field of public life."
This happens in other parts of the world, too, of course. I once asked a girl in college if she was from India; she gave me a hateful death stare and coldly declared that she was from Bangladesh.
There certainly are many instances of people hating ethnicities very disimilar form them, but that happens after people from different parts of the world migrate close to each other.
I suspect that proximity has a great deal more to do with it than similarity. If your neighbor is actually significantly different than you (ugh, the weird smells from the strange food those people eat!) I would think it makes it even worse.
* Russians (russkiye), an ethnic group of the East Slavic peoples, primarily living in Russia and neighboring countries (where they are also known as Ruthenians or by other names)
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Close enough?