Douglass, who was, in my opinion, an authentic American genius, does not merely denounce slavery and slaveholders in his autobiography, but he consistently and eloquently points out the soul-damaging and distorting effects of slave ownership on the whites themselves.
In one such example, he points to Sophia Auld, the wife of one of Douglass' owners who, in the beginning, extends kindness to him and teaches him letters, the first steps towards Douglass' literacy and ultimately, the ticket out of slavery for him. Once her kindness is discovered, her husband, Thomas Auld tells her to stop in no uncertain terms. She becomes cold towards him, and in so doing, Douglass argues that Sophia Auld lost her soul, surrendered her generosity of spirit to slaveholding itself, and thus, corrupted herself.
He also points out the obvious contradictions in being a slaveholder and supposedly a Christian and that, by owning slaves, whites had forsaken their own religion and God.