Slavery was one issue but it was mainly an issue with respect to the extension of slavery into new States and territories. If you disagree with that, you need to do some more factual reading.
I didn't say it wasn't an issue, nor am I trying to "minimize" it. I said it was ONLY one issue an not the determining one in sucession. That's an opinion from my readings and one to which you are apparently vigorously opposed.
Unfortunately for your side of the argument, there are very few, if any, true scholars of American History and the Civil War that agree with your "single issue" viewpoint.
A cusory study of the Abolition movement would show you that it was indeed a minority movement, opposed even in the North. That remained true even after the outbreak of hositilities and there are contemporary newspaper articles and editorials that show that.
The South and tariffs? Your example is of the South as an exporting economy. First, the tariffs were applied to IMPORTS. The South, with nearly no industrial capacity exported relatively inexpensive raw materials and unfinished goods. They IMPORTED expensive finished goods. The tariffs on IMPORTED goods, in those days before the Income Tax, were almost the sole source of funding for the Federal government. Research will show you that the South was paying an extremely disproportionate amount of the bill, much to the delight and benefit of the North.
As Laz pointed out, slavery in the South was failing economically. It would have eventually died out on it's own because it simply was not "good business". Someone else pointed out that the overwhelming majority of Southerners owned no slaves at all.
States rights? It wasn't in the least about "local customs". Again, in your mono-vision, the only thing you can see is slavery. Please take a look at the changes the Confederates made to the US Constitution when writing their own. It's an easy web search.
I think there you'll find the true "states rights" issues that they felt were not being correctly handled by the Federal Government. It's very important to note that the Confederate Constitution did not change any of the original US Constitution with respect to slavery. For example, the U.S. Constitution ended the importation of slaves after 1808 and the Confederate Constitution simply forbade it. Both constitutions allowed slave ownership, of course. Seems funny the Southern Constitution would forbid the importation of slaves if the war was only about slavery, don't you think?
Again I'll say it. Slavery was indeed an issue between the North and the South. Primarily, it was an issue with respect to the extension of slavery into new States and Territories. But it was only one issue, certainly not the most important issue and not the determining one in sucession.