Why are only Western nations committed to immigration and diversity?

Why would an entire people commit itself to its own dissolution. Is not the supreme principle of Darwinian theory the struggle not only for individual survival but also survival of one’s group, which entails an ethics of in-group cooperation and out-group derogation? How did it come about that such powerful instincts for in-group preference and loyalty have come to be seen as odiously racist amongst Whites, whereas in-group preference is taken for granted in the rest of the world and, more insanely, special group rights are legally sanctioned for minorities inside Western nations? http://alt-right.ca/5MkM3