I think this is a fair question. I think it was predominantly white men. Never heard of a black man named Richard being called Dick. I think they usually use Rick instead.
I never got used to Richie Allen requesting that he be called Dick Allen https://www.baseball-reference.com/players/a/allendi01.shtml. I had no preference, but as a Phillies fan I had heard him referred to as Richie Allen a zillion times his first few years on the team so Dick Allen always clanged off my ears.
