I think it's only human nature to look negatively at those with perceived differences. Look at India with their caste system. Those in the upper castes wouldn't dare associate themselves with those in the lower castes. And they're all from the same culture/race!

It's always more shocking when it happens to those close to you. My uncle disowned my cousin when she married a man from Pakistan (they're Japanese).

I remember this one job I applied for, I was told I wasn't "Japanese enough" (I'm half).