In the letters of Robert E Lee you find the idea that if the whole issue had been to obey the Constitution of the USA there never would have been any conflict. But you find the exact same idea in General Grant. To both of these men the entire issue was this alone. The South held secession was a right. And even if that is not a part of the Constitution , still it was stated openly by the Virginia delegates to the Continental Congress].
However in terms of slavery, I think the welfare system in the USA is slavery forcing white people to work for blacks without compensation. So I do not think that anyone really objects to slaver. Rather slavery of blacks they object to. But slavery of white people is OK.
But that is how things are in the West--with the newspapers advocating one kind of outrage after the other. First global cooling, then global warming. Then Climate change, then vaccines. One set of outrages after the other. That is the odd sort of mentality of the West. Every ten years or so, the absolute unchangeable morality changes from one thing to the other, and that other is also unchangeable while the first is forgotten and goes back to the regular state.
Rather I think that morality ought to be based on reason, not fads nor just "faith" which is often delusion.