There is an ingrained bias for what you can call a European body type in classical ballet -- it's been a part of the development of the art form. We are, gradually, shifting away from those assumptions, and accepting a wider variety of bodies in ballet, for which I am grateful, but we are not at the finish line yet. Someone can certainly prefer the 'historical norm' but unless they recognize that it comes with inherent biases then the possibility for racism, however unintentional, is certainly there.
While I agree that there are many factors other than racism that contribute to the lack of black women in classical dance - lack of access, few black role models, cost - I feel that body type is probably one one of the elements that is emphasized too often.
Yes, most African American women are of West African decent, but it's not like that racial subgroup consists of only one heavily-muscled athletic build.
As the saying goes, "I've been black all my life," and I can assure you we have our share of ectomorphs who eat like lumberjacks and still look like Alex Wek.
Unfortunately, I'm not one of them. And those who are willowy or any other shape, don't seem to think about ballet