also, everyone remember: the first wave of seccession (south carolina, alabama, georgia, florida, mississippi) was certainly and undoubtedly brought on primarily by the slavery issue. specifically, the perceived threat of abolition of chattel slavery- a tyrant Lincoln indeed was but he was nothing like the abolitionist he was painted as throughout the south.
I think it was more a matter of honor for South Carolina. They clearly believed they were in a Union that enabled them to run a completely free and independent enterprise or they never would have joined the colonies in the revolution. Also although slavery was the breaking point, it is a matter of honor when someone not from your own turf suddenly tells you what you can and can't do, they threatened secession before over tarrifs.
https://en.wikipedia.org/wiki/Nullification_CrisisAs a Southern Gentleman it was overtly offensive to be told what to do, it's an affront to your own masculinity, especially after leaving the British Empire for that very same reason less than 100 years earlier.
Honor was something Yankees no longer possessed, the scheming lying thieving bastards always profited off the back of slavery indirectly while shaking their finger at the South. Manufactured textiles made a much larger profit off of slave cotton than the plantation owners, plus they were aided by the government who maintained a "Yankee friendly" tax policy on those produced goods while attacking the source that made it all possible.
The newly formed Republican party in the United States was also viewed in the South as something like the Green party is now, third party lunatics. Lincoln's name didn't even appear on the Presidential voting ballots in 12 of 13 Southern states, so this was a major shock that someone who doesn't even show up on the voting ballot part of a newly formed radical political party is now your President. Their entire political platform was based on being Anti-Southern, enabling high tarrifs and Federally subsidized Northern economic growth (communist in nature) to raise national debt, basically they wanted the South to pay off their government loans thru tarrifs, taxes and National debt so they could further compete with Europe industrially.
Freeing the slaves only entered the mind of Yankdom years after the war began after they realized they were not going to win an honorable white man's war vs the South.