You know some overseers were black. To trot out a black man to show that their ideology is not white supremacists is a little typical. That is the definition of I can't be racist because I have a black friend.
When I was in 4th grade riding the bus in Chattanooga, TN there was a guy who was friends with me and my brother riding the bus too. He was older than me but younger than my brother. He was talking to one of his white friends and was talking about a black kid that went to Tyner High. I heard him say the n-word. I looked at him, and he said I am not talking about you. You are not like him. I say that to say, that most racists have black friends/people that they like because they know them. Does not make them less racists, they just happen to know and like a person of color.