Can diversity be a bad thing? Racist people, why do we need to keep the races pure?

Can the fight for diversity turn just as ugly as the fight for white supremacy? Suppose a mixed race dictator rose to power and started killing all purebreds. Only families of interracial relationships would be safe. The KKK and Black Panthers would have to join forces to defeat him. Nature seems to crave diversity but it also breeds chaos. However, through the madness it also grows stronger as it adapts. Smarter as it learns from its mistakes. This is why sexual reproduction has an evolutionary advantage over asexual reproduction. Why do we as human beings want everything to be the same? Is it just for the sake of comfort? The irony of mixing together is that in the end, we all become part of a whole and therefore are collectively the same. Should this be the goal, separate but equal doesn't seem to work? Ultimately it's about comprise. Everyone loses something, but in exchange we get to live in harmony with each other as a result.