That may be the issue.
The owner may have not clearly set the rules about which music should be emphasized. He could have asked for a general mix of pop music.
The black manager may have used his own discretion to play more hip hop because that's what HE liked.
Face facts. Hip hop will attract a specific clientèle just as country & western or heavy metal would.
If the manager was stressing hip hop and the clientèle changed dramatically I can see how the owner may take issue.
If that's the case the owner should have made it clear what music he wanted played in his bar. He didn't have to give any other reason than to say it's his bar.
The manager was white. It says so in the article.