My own take is that being a descendant of slaves makes no difference when it comes to perceptions of whether or not this or that person is "black," as the term applies in the states.  Being black is, as you know, as much a cultural thing as it is a biological thing, which is a point on which some black leaders (the black Villagers, sans Clyburn and Lewis) and a lot of really stupid white journalists -- looking at you, Wolf Blitzer -- didn't "get" it.

Be nice to America. Or we'll bring democracy to your country.