Segregation is alive and well. It just targets different populations using different criteria. Segregation is a basic component of cognitive function. We designate reality with words and assign what we perceive to groups. It’s not necessarily an antagonistic process. After all, when we separate white and brown beans we do it to get groups of the same kind, to enhance the flavor instead of having them mixed.
So, I’d argue not only that segregation will persist as an habitual human behavior, but that the antagonism we decry actually arises from another common behavior — i.e. the impulse to exclude and/or destroy whatever and whoever doesn’t immediately satisfy. I don’t think exclusivity is universal. After all, if it were, there’d be no progress or exploration because humans would shun anything that’s different. Which suggests that exclusivity, shutting the unfamiliar out, is an aberration which may be endemic or learned. Or perhaps an antagonistic attitude is a milder form that leaves open the door to acceptance instead of going right for rejection and the impulse to destroy.
That said, exclusivity seems to be pretty much a prejudice, whether born to or learned. That is, it precedes logical thought and cognition. To pre-judge is to rely on an emotional response. Pre-judgement is not, like a pre-wash, well thought out, but probably as hard for a spot to resist.
“Out, out damned spot.” Was that addressed to a prejudice?