Would not prejudice and bigotry still exist if you reduced the planet to one nationality?

Often some people, maybe many, believe if the planet was populated by all the same nationality or race of people, bigotry, and prejudice would go the way of the T-Rex, is that really so? India still has a caste system when they are basically one nation with few permanent foreigners. What if you reduced it to all Chinese? I read in China if you have certain features that seem more Western you were looked at as better, more appealing, (could not find the info to link to it). What if the US was reduced to all people of European descent would there be no prejudice or would the Blondes start to cobble together against the brunettes who in turn look down on the redheads?