Without incurring kneejerk indignation (or one of Daveman's dancing Hitlers), is it racist, or indeed, morally repugnant to (within the law) go out of your way to restrict yourself from interacting with people who don't belong to your race?
Of greater concern would be why one should feel the need to do so.
It's not a need but rather a natural inclination and there is nothing racist about it.
I am White and while I generally prefer to associate with intelligent Blacks rather than stupid Whites, all things being equal, and as with any other type of animal, I naturally gravitate toward and am more comfortable with people and things which are most familiar to me.
I was born and raised in Brooklyn, New York, which was a "city of neighborhoods." Bensonhurst was predominately Italian, Flatbush was mostly Jewish, Park Slope was mainly Irish with a small Bohemian enclave inhabited by a variety of ethnicities, Bay Ridge was Nordic and German and Bedford-Stuyvestant was Black -- and that, too, was divided by a section which was exclusively West Indian. These divisions were not imposed by any mandate but occurred and existed as a matter of preference, the best example being that of Black Muslims who are absolutely adamant about living apart from Whites. It should be noted that people got along very well in Brooklyn. Even during the era when Jim Crow was active in the South it was unheard of in Brookyn.
Such formations are not uncommon. Chinese, for example, are known to form Chinatowns wherever they settle in America (and probably elsewhere) and they generally do not socialize outside their ethnicity. Likewise, Orthodox Jews tend to form insular communities and keep to themselves. It's not because of ethnic antipathy but simply because of a natural preference for what it most familiar. Opposition to this natural tendency has come about as the result of intense pressure imposed by
political correctness.
But
Birds of a feather flock together.