Blackness is a political category, historically produced through oppression. No oppression, no "race." Therefore, unless you want to tolerate a hypothesis that genes are responsible for the political oppression that blacks suffer, you don't want to tolerate a hypothesis that "race" is a biological category, which can account for differences in intellectual achievement. To counter scientific racism, one must oppose naturalization.
BTW, making a fact-value distinction doesn't really help combat oppression:
***** ...Singer contends that the equation of ethics with equality is not willful or partisan but a necessary inference from the ethical point of view. "Equality," he declares, "is a basic ethical principle, not an assertion of fact," which is his way of saying that equality inheres in the very logical structure of the idea of ethics. All arguments that instead attempt to find the basis for human equality in some empirical quality of human nature--intelligence, rationality, moral personality--are doomed, according to Singer, because these qualities can always be seen to be unequally distributed. Never mind that thinkers such as Hobbes, Locke, and Kant argued that equality can be derived from human nature or our nature as rational beings on the grounds that it is the capacities, which are essential, that are morally relevant, while the differences in capacity among members of the species are too slight to be of moral significance.
In any case, Singer is certainly correct to argue that differences in talents and abilities do not in themselves justify an inegalitarian political order, because "there is no logically compelling reason for assuming that a difference in ability between two people justifies any difference in the amount of consideration we give to their interests." Yet Singer is quite wrong to proceed as if this observation provided an argument in favor of egalitarian political arrangements. For what Singer fails to point out is that there is also no logically compelling reason for assuming that a difference in ability between two people can under no circumstances justify differences in the amount of consideration we give to their interests. On the question of human equality, logic is strictly neutral.
...Singer himself maintains that equality cannot be grounded in human intelligence, moral personality, or rationality, because such qualities or capacities are unequally distributed among human beings. If rationality and self-consciousness nevertheless define the morally significant person--as Singer insists that they do, in his case for animal rights, euthanasia, infanticide, and abortion--then why shouldn't greater rationality make you more of a person, or a more valuable person, an individual entitled to a greater proportion of society's scarce resources?...
Peter Berkowitz, "Other People's Mothers," _The New Republic_ 10 Jan. 2000
[Peter Berkowitz teaches at George Mason University Law School and is the author most recently of Virtue and the Making of Modern Liberalism (Princeton University Press).] *****
In fact, oppressions under capitalism work through the realm of "facts."
Yoshie