I agree. I see quite a bit of black racers down at my FL house. My Neighbor told me we have pygmy rattlers around. But with the blacks there I haven't seen any of the little rattlers.
My friend had a farm up the road here in PA and he had a very big black snake living in his barn. I saw it on several occasions. He never bothered it and it never bothered him and he said he had no problems with rats. But it was a bit eerie having it sitting on the rafters above you while you were working in the barn.