Both black and white are very commonly lower-case. For example in the Bloomberg article, they refer several times to "black person's" and "black." I consider it incorrect to upper-case a racial identifier if you're not going to upper-case them all. I alternatively could upper-case Black and White, however I also consider that wrong, and borderline stupid (again, my personal opinion).
If I were referring to a specific national heritage, I would upper-case. Vietnamese American. Nigerian American. German American. And so on.
I also would not upper-case "a Tall American" in description of someone. A person that is an asian American is not necessarily from Asia, asian is their race. A person is not from "black" or "white" either. It's as ridiculous to upper-case asian in this use, as it would be to upper-case Brown Eyed American or Green Eyed American or "the Freckled American."