Your post is a perfect example of judging people who lived generations ago by today's values. Turn it around, and we all burn at the stake for witchcraft, paganism, heresy, apostasy, and worse.
The question I keep coming back to is, why is it so important to you guys, to make the South wrong about standing up for their rights?
Don't you see that someone else can play the same game with you some day at your show trial, and try to get you to "confess" to the "crime" of having owned firearms? Of having committed thought crimes?
You're indulging in revisionism -- as much as we talk about revisionism around here -- and setting yourself up for a fall. What's in it for you that is so attractive, that you'd go for the cheese of moral relativism and teleological "truth"? That's a mug's game, a "gotcha" game for motivated losers. You make yourself a prey for Stalinist bear-baiters and the kind of ugly games Solzhenitsyn described in The Gulag Archipelago, as Stalin filled the Gulag with "wreckers", "capitalist roaders", "gold bugs" and other Enemies of the State, most of whom had long resumes as dedicated, true-believing Bolsheviks. And you want to play?
If the South had an legitimate case to make, it would be a different matter, but they didn't.
Their case then was pure and simple: they declared their secession, not because of what the Federal government had done, but rather out of fear for what it might do against slavery, under the new Abolitionist Republican government.
So none of the previously established criteria for dissolving the Union had been met, and yet the South seceded anyway -- in Madison's words, "at pleasure."
Then they provoked war, and the rest is history...