Every high school student should have some level of this program. The four kids I coached want to major in military science, chemical engineering, pharmacology and genetics. No lawyers. But you should have heard them quote de Toqueville, Federalist 78 and Chevron Deference when they delivered their paper on judicial review.
The other argument I have seen a lot is that Lincoln and the dastardly Republicans want to deprive the slavers of their "property," which is a gross violation of their constitutional rights.
I have read a couple of attempts to construct a Bible based argument for slavery, but its just a mishmash that makes no sense at all.
I agree, the entire system had to corrode the values of that society.