A while ago, I came across this entry in the American Heritage Usage Dictionary (I'm an English major; we use these):
Black is sometimes capitalized in its racial sense, especially in the
black press, though the lowercase form is still widely used by authors of all
races. The capitalization of Black does raise ancillary problems for the
treatment of the term white. Orthographic evenhandedness would seem to require
the use of uppercase White, but this form might be taken to imply that whites
constitute a single ethnic group, an issue that is certainly debatable.
Uppercase White is also sometimes associated with the writings of white
supremacist groups, which for many people would of itself be sufficient reason
to dismiss it. On the other hand, the use of lowercase white in the same context
as uppercase Black will obviously raise questions as to how and why the writer
has distinguished between the two groups. There is no entirely happy solution to
this problem. In all likelihood, uncertainty as to the mode of styling of white
has dissuaded many publications from adopting the capitalized form Black.
Interestingly enough, I recently learned that to be completely grammatically and politically correct, the capitalized Deaf is supposed to be used any time one is addressing the Deaf culture or community, just as you would capitalize Asian or Mormon. Although it is an issue that is completely separate from the capitalization of black, I still find it fascinating that a simple thing such as capitalization can cause such a controversy, but that seems to just be the way it goes when it comes to racial and cultural identity. All in all, I'm personally okay with using both black and white in the lowercase, as long as the context is clear enough. Also, I agree with the fact that the word white can't be used to describe a single ethnic group, though I wonder if that also means that the same restriction must be applied to the word black. Since I don't have a single ancestor from the African continent, I don't feel qualified to give an answer. Maybe we should just give up using the words black and white in a racial context altogether?
Regards, best wishes, and quandaries,