If I'm the Celtics, I'd get Bill Russell on the phone asap. He led a boycott of Black Celtics and Hawks players in 1961. https://twitter.com/celtics/status/1298338354854014979
In 1964, when asked if he'd retire to fight for civil rights, he said "Yes, but only if it would make a concrete contribution. There’d be no choice. It would be the duty of any American to fight for a cause he strongly believes in.”