[carapace]

Africans enslaved in America effectively had their original cultures denied and destroyed. That's why it's appropriate to capitalize Black but not white when referring to American subcultures. (Whiteness isn't genetic. E.g. in South Africa under apartheid Chinese people were legally black but Japanese people were legally white.)

[_-david-_]

Various whites had their cultures denied and destroyed as well. By your logic White should capitalized as well.

[carapace]

Which "various whites" specifically?

[_-david-_]

Slavs where taken as slaves and is where the word slave derives from.

[carapace]

We capitalize "Slavs".

(FWIW, Slavic culture didn't originate with the enslaved Slavs.)

[_-david-_]

Then we should also capitalize White as well as Black.

[carapace]

That doesn't make sense. There is no one "White" culture, so when you capitalize the word in the context of United States of America it refers to the KKK et. al., not to mainstream American culture, which developed in waves of lots of different cultures (not all of which are European-derived.) E.g. the Irish. Treated like shit when they first got here, now we have St. Patrick's Day parades. And so we have Irish-Americans, Italian-Americans, Chinese-Americans, and so on. They kept their cultures.

Now when we talk about African-Americans you gotta remember that Africa is a huge continent, not a single nation or culture. The people who were kidnapped, beaten, chained, subjected to the horrors of the Middle Passage, then treated like subhumans for hundreds of years, they came from many different cultures, they were forcibly prevented from carrying those with them, and so they have formed a new culture, native to the soil of this continent. That's why it's appropriate to capitalize the word "Black" when referring to Black American culture: it's a proper noun.

When you speak of "white people" in America, you're generally referring to the whole American mainstream culture, which is neither genetically nor culturally Caucasian exclusively. The word "White" capitalized as a proper noun refers to a specific complex of "White supremacist" culture.

In sum:

Black - African American

white - Mainstream American (includes everybody: The fictional character Steven Quincy Urkel could be called "white" in this sense.)

White - racist American subculture