The point for our discussion, perhaps you will agree, is that those portions of the world making some serious effort to conform their practices to moral law and justice, i.e., Christendom, did eliminate slavery. And they did so as part of what Tocqueville identified as the irresistible force of the doctrine of human equality. The thesis of his book, Democracy in America, is that the tide of human equality was sweeping over the civilized world, and that rather than resist it, the old world should take careful thought how best to order affairs in light of it. I would be interested in what others who have read the history of this time would say about the thesis that emancipation in the British and French empires was entirely an economic phenomenon.
I think the point is that the South was unique, certainly among peoples tracing their political institutions to the Western or Christian civilization, in making a deliberate decision in the 19th century to embrace or defend slavery. In this, they departed diametrically from any society with whom they shared traditional or intellectual connection.
I would say it was an attempt to rationalise, to paint the decision by the souths slaveholders in a better light. -- That once they came to their economic senses, they too would have emancipated.
It is almost a textbook example of being banal about evil, imo.