I sense you referencing John Derbyshire’s “the Rules - For White People”, as one of the tenets is to avoid groups or conentrations of black people, and also to avoid black people not known to you personally.
I never heard of what you reference.
Derbyshire’s rules, or the white version of “The Talk”, are words to live by, and I mean that literally. If everyone got their just desserts on this earth, the man who fired him would be a victim of his own stupid political correctness by ignoring those rules.