yeah it's a positive thing that you're actually observing that people do sort themselves out on the basis of race but you may be very off on the reason for why they do it
the 'fear of differences' thing is sort of a progressive pablum line that nobody really analyses correctly
when left to themselves people just generally prefer the company of people like themselves
we would rather associate with individuals who are like us and there is likely a genetic basis for PREFERRING people who are like YOU
human beings are essentially tribal animals that sort themselves into groups many of which are simply constructed (like nations, sports teams, school pride, town pride, etc) and many of which are biological like one's racial sub-group, family, etc.
basically its looking more and more likely that human beings and animals in general tend to be more altruistic towards not only their kin but their non-kin who share a larger portion of their genetic material