I have never been ashamed to admit I had ancestors who owned slaves, as well as ancestors who were considered white trash. I am an extension of them. I am the sum total of all who have come before me. If I have learned from the mistakes of my ancestors, I have nothing to be ashamed of.
It doesn't matter what they did. What matters is what I give to my children to pass on to their children.
You are the first to admit it and I congratulate you. Considering that it was a perfectly leagal practice and accepted by the majority of Americans at the time I see nothing to be embarassed by it. It was legal when they owned slaves and the stopped owning them when it became illegal. Case closed.