I get that's the part that would anger the most people and within the context of black artistry it makes perfect sense to that audience.
I'm going to get far more philosophical on this subject than I normally do but I don't expect any agreement. Not because you or anyone is close-minded but because I think differences on this boil down to fundamental differences in how people see this world. Opinions they formed long before they could rationalize the subject and that flows in both directions.
There is a general opinion within the black community (and if you're black, understand I'm not trying to speak for you) that as Paul Mooney put it:
That America is perfectly comfortable taking elements of black America, copying it, incorporating it while simultaneously denigrating the creators of said elements. Now, there's 2 sides to that and Williams addressed part of it in the previous part of his speech re: branding of their bodies, chasing money, etc. A clear message to those black performers that they've undermined their community's standing via a desire to make commodities of themselves.
But the part here about black gold, burying black bodies out sight, etc. is a reference to how black art and black ideas can become celebrated while the people themselves don't share in acclaim. Hip hop is probably a decent example. Non-black people can put on the clothes, copy the slang, duplicate the music and celebrate all of the elements as something wonderful (realizing of course that plenty of people aren't hip hop fans) while simultaneously dismissing the culture that created hip hop as something uniquely and negatively black - emblematic of a debased pro-crime, anti-family, irresponsible culture.
So they extract the culture for social purposes while burying/dismissing/discarding the larger black social contexts that created that culture. To the black community, for which hip hop encompasses far more than the just the mainstream element that appeals to the most fervent consumer base (primarily not a black consumer base), it's a bit of a slap in the face. The mainstream won't adopt the messaging of more socially conscious rappers or singers to celebrate. It's a lesson that black artists need to be reminded of. That their messaging matters because the message you're selling (branding onto your body) isn't actually being used to raise the community just because you got paid to sell it.