As regards slavery, there existed a contradiction between our original Constitution and our Declaration of Independence. The Declaration described us as being created equal and bearing natural rights granted to us by God, our Creator. Our original Constitution was tolerant of slavery and thus in conflict with the Declaration on that one point.
I side with the Declaration as regards that conflict. However, it must be acknowledged that slavery brought many Africans to Christ.
And, the South was probably on solid legal ground in seceding.