... if he expects people to not compose music that reflects their own upbringing and background, he's fighting an uphill battle. The BB's were raised in suburban, mostly-white middle class California. So they're going to write music that reflects that upbringing. So what? What does he expect? If everyone who pretended or purported to perform what we call "Rock Music" all performed music that sounded like Chuck Berry or BB King just to assuage some sort of racial conscience, it would all sound the same and we would lose a lot of variety.
You're dead-on. It's a touchy subject, and I get why, but this is a damned-if-you-do, damned-if-you-don't proposition. To stay within one's culture, that's racist by propagating the dominant culture. To imitate minority cultures is very widely panned as cultural appropriation. Real artists almost always do some of each (in the good sense, not the insulting sense).