I understand that. But the reality of it is different for most people. There is a perception of lack of fairness if an all white jury convicts a black teen in the murder of a white man. I've never heard of an all black jury trying a white defendant, but it would be the same either way. You don't have to agree or like it, and the jury is almost certainly doing their best to be fair, either way. But if I'm a black teen, I would prefer a mixed jury to an all white one.
It's a matter of location. I live in a very rural county where the black population is less than 1%. If a black man were charged with a crime that warranted a jury trial here, he's getting an all white jury, because that's what the jury pool dictates. It would be diverse in terms of male/female, but that's about it. That's the nature of farm country.