Your [0][1][2][3] use those same systemically-erroneous tests (click through and look for 25). To me, this confirms that the problem's endemic to the system of medicine.
In general, it seems that you believe that we well-understand vitamin D and thus clearly the situation is that there's a difference between white and black people. To me, however, what the situation says is that we poorly understand vitamin D! We've taken something that seems important because it was historically important to white people and tried to extrapolate it cleanly to all people, but it first needs to be cleaned of the racist lens. Indeed, from your [1], "Data on vitamin D levels in healthy African adults is scant."
From your [3], vitamin D levels are experimentally low in African-Americans and Hispano-Americans. Occum's Razor begs us to justify why this isn't a race-poverty correlation, yet another indication that our society is systematically disenfranchising folks based on skin color and country of origin. With better diet might come better vitamin D blood levels.
You know why this sort of research is ammunition for racists, right? It's because racism is the belief that humans don't form one single species. By considering African-Americans as having exotic genetics, research like what you've linked implicitly and directly backs the racist agenda.
Finally: You seem to think that racism is something which tars and stains people, but that is from the same bogus essentialism that spawns racism itself. No, it's a series of beliefs about genetics, and those beliefs can be refuted. The reason why racism is a "serious accusation" is not because of some danger of ejecting valued contributors from the community; it is because it leads directly to people being shot in the street, sterilized in concentration camps, harvested for organs, etc.