I was born and raised in Illinois, the "Land of Lincoln," and was taught as all Illinois schoolchildren are to venerate the Union and excoriate the horrid slave-driving Southerners. But when I did graduate study in history in the archives of the University of Illinois, I began to see things differently. I've come to believe that if it was okay (nay--heroic! noble!) for the American colonists to make war on and demand independence from Great Britain, which asked for little enough from them in exchange for protection, then the Southern people who wanted to govern themselves had every right to do so as well. If a people want to govern themselves, they should have the freedom to do so. I don't consider that "destroying the country" since the United States would have still continued to exist, its government and laws unchanged, if the South departed.
You confuse the principles of the mid-nineteenth-century Democrats with those of today. The Democrats of the 1860s favored minimal government interference, supported an agrarian economy, and disliked a strong central government. In particular, they loathed paying high taxes (in the form of tariffs) to a central government when they did not receive compensatory benefits. The modern Democrats of course espouse just the opposite views. I fully support your hatred of modern Democrats, but nineteenth-century Democrats shared many of the opinions of modern conservatives.
Even if separation were the only solution, there were all manner of practical questions to resolve and they ought to have been handled within constitutional channels. I suppose most Americans at the time would eventually have let those Southern states that wanted to leave go, but the formation of another national government, the call for a mammoth army, the repudiation of debts, the seizure of federal property and the assault on Sumter constituted a chain of provocations that couldn't help but bring war.
There was much bravery and virtue among many who fought for the Confederacy -- as among those who fought for the Union -- but the political leaders who launched the rebellion aren't to be celebrated. Their motives were hardly laudable and their methods were not the best either.
Rockwell is a con artist. He seems to assume that had the Confederacy suceeded we would have much greater freedom without forfeiting all the benefits of union. No one can say with authority what would have happened, but I think he's wrong on both counts. Whether we would become two hostile governments struggling to maintain their authority or a dozen smaller squabbling countries, it's not at all clear that we would be freer than we are now. Had Davis won it's entirely possible, that we would be poorer, more divided, more hostile towards each other, less secure and less free.
History is a fascinating subject, and there are few periods of our history of greater interest than the Civil War, but Rockwell had done us a disservice by reopening old wounds.
Did the black Southern people get a chance to vote for seccession?
White Southerners were willing to fight a war for independence. What if Lincoln had said, "I'll grant you independence, if you exchange places with your slaves." Would white Southererns have paid that price for independence? No?
Yet it was the price they demanded of black Southerners.