I can imagine that if I were a black parent I might well want to live in a neighborhood where my children would face less pressure to get involved with gangs and that I might conclude that a majority-black neighborhood was suboptimal in that respect. That is why I hesitated to categorically call it racism.
That does smell like racism but I'm not sure it is in all cases; a native Chinese speaker might prefer to live in a city's Chinatown without them being racist.
Is it? On the other side of things, might black people want to avoid majority white neighborhoods where the white police will more likely target them as well? Might black people prefer black neighborhood themselves so that they can live amongst people they understand with a culture they're familiar with? Are those black people racist?
Freedom of association is important for all people, I believe. If Asian people have been victimized by other groups in American society, they should be allowed to congregate and live with each other, where they will be able to have the power and influence to protect their people and interests. If black people cannot trust the white police force to not kill them, they should be allowed to move to black cities with black police who will less likely kill them. And if whites feel that they cannot live amongst blacks due to their poor relations with eachother, who are we to stop them from leaving? Because forcing two opposing groups to live with each other only breeds more violence and suffering. I wouldn't shame them or call them racist. It's pragamatism at worst. You could bring up statistics all you want to say why x or y is not the case. But that doesn't matter to individuals. People decide these things on their own, in their best interest, for their family's safety.