As a recovering freelance writer, I question this. This is not to say you are incorrect, but the races/groupings in question are Negro and Caucasian. The words "black" and "white" (modifiers) are colors which, as fair as I know, we don't capitalize*, e.g. the Purple plum, the Green pencil, etc., and yet we (are expected to) write "the Black man", "the White man" quite frankly it's more along the line of "the Black man", "the white man".
This is why I wondered if this practice wasn't rooted in PC-ism.
*(We don't usually capitalize.)
I capitalize it out of respect, then.
And if I were being PC, then this discussion would be academic. I would refer to Blacks as "African-Americans," or whatever tag the chic are using this week.