As I say, let's see those declarations. I'd like to see the ones that offer the tariff as the reason for secession. At the time of secession, the tariff was at the 1857 rate, and Democrat President Buchanan was calling for the passage of the Morrill Tariff bill, which he eventually signed, not Lincoln.
But, really, rather than open the door to all the "tariff" sophisms, why don't you just see if you can find one state that offered the tariff as the reason for leaving?
You must not be so quick to apply our ideas to the past. We are, at least theoretically, against slavery. We think it wrong. (Though our government goes out of its way to toady to countries such as Red China and Saudi Arabia where slavery is still practiced.) But that was not the view for most of human history. Slavery was an accepted practice and had been on every inhabited continent. Slavery was on the way out in the Western world -- though it is still practiced in much of the world today. Most of the western world achieved emancipation peacefully. But that was not even tried here.
I don't know what you mean to suggest here, unless that the Declaration was not understood to apply to all men, but only white men. Lincoln famously said that there was no man on earth who thought, at the time of the founding, that "all men" meant "all white men." He dared anyone to find evidence that this was so.
But be serious. The northern states "achieved emancipation peacefully," so I don't know what you mean by "that was not even tried here." It was repudiated in the most solemn way as even an ultimate, distant goal by the Southern states who cast their lot with a regime based on slavery, after they had almost a century to think the matter over carefully, and while the rest of the world moved toward emancipation and substantially accomplished it. The civilized world of 1776 was very clear on the moral issues involved in slavery, and the civilized world of 1860 was even clearer -- the South just ILLEGITIMATELY DISAGREED. And they quite openly based their revolt on that disagreement. So let's see what statements by seceeding states you have that a) offer reasons for the justice of secession as an avoidance of tyranny, and b) don't make slavery the principal, even only, cause of secession.
Actually, as pointed out, the whole of the world didn't move away from slavery. It is still alive in much of the world. Africa, the Middle East, much of Asia still practices slavery. Unfortunately, we have a long way to go before we eliminate slavery.
In the places where slavery was abolished, it was almost without exception done peacefully, generally through compensated emancipation or through phasing out slavery over a period of years. And while the Psalms singers like to take credit for ending slavery, it was really simple economics that did the trick. Owning slaves just didn't pay. (We might as well face facts, for many people, if not most, money counts for more than morality.)
Don't think I am defending slavery or defending the South's stance on slavery. But this is not a question of whether slavery was right or wrong. There's no question that slavery is wrong. It is a question of whether people may decide what kind of government they will live under.