BTW, there were a great many blacks who were not only slave holders but loyal confederates in the Old South.
I love how the defenders of the Old South love to point out how there were just tons of black slave owners, but then point out that only about 3% of the people in the south owned any slaves at all. Cracks me up.
Yes, there were freed Americans of African heritage who owned slaves, but there were either ih Louisiana where there families had been freed from slavery under the French, or they were likely blood relatives of white slave owners. In addition, after the Fugitive Slave Act of 1850 made it legal for a white southern to re-enslave a free black, a lot of free blacks sold themselves back into slavery under one of these white blood relative types so that they couldn't be taken off the street as a free man.
As for the question, it's actually rather hard to consider the ante bellum south's slave owners as Christians in any case, but christianity does accept sinners, so we must. God's judgement may be different. The greatest and most cruel slavers in history though are the secular states of Europe like Germany under Hitler and the Soviets under Stalin.