I can certainly understand your feelings about the behavior of your ancestors, but like you say, you only have control over what is in the here and now.
One of my African-American cousins asked why I had Confederate flags on the listings of some of my ancestors. I responded that I marked those who served in the Confederate forces with a flag in the same manner as I marked those who fought in the Revolutionary War or the War of 1812. In doing so I am not celebrating slavery or its evils but simply acknowledging their military service. If I had any ancestors who fought for the Union, I would mark them accordingly too.
Ironically the ancestors who served in the Confederate military were probably the most likely candidates to be the common white ancestors that I share with my African-American cousins. Those who were willing to fight to preserve their slave-owning way of life are certainly the first ones that I would look to.
It is always difficult to confirm an actual relationship between a slave owner and a slave who might have born him a child but occasionally there will be mention in a will of special provisions being made for a particular female and her children. Unfortunately such things are quite rarely seen.
The other problem is that even if you are fortunate to be able to narrow down things to a particular geographical location or even a family, it is still very difficult to show that a particular slave-owner fathered a child when the child's father could have always been the owner's brother, son, nephew, etc. That was the problem with the DNA tests involving Thomas Jefferson. They could prove that a Hemming child was fathered by a male Jefferson, but not necessarily Tom himself.