Ah Tommy and his tariff. I'' tell you, you're going to have to do a whole lot better than Tommy DiLusional. Let's start by asking this question. Tommy places great importance on the party platform, and says "the protectionist tariff was a key plank." Actually it was number 12 of 17, hardly a key plank, but regardless of that if the tariff was such a burning issue in the South then why does neither Democratic platform even mention it? Neither the Douglas faction OR the Breckenridge faction ran on a platform that mentions tariffs at all. Both platforms call for conquering Cuba and a transcontinental railroad. Both support slavery in the territories. But neither mentions tariffs, much less condemns them. Why is that, do you suppose? If tariffs were such a burden?
Why, if tariffs were such an anathema, did the confederate congress pass a protectionist tariff right off the bat, in May of 1861?
So if tariffs explain Lincoln's motivations then what explains the southern actions?
Look non, if you're so delusional as to think that one half of this nation fought the other half to free slaves on human rights grounds, I can't help you. It was a massive power grab by northern state interests that really had nothing to do with northerners themselves (i.e. - they not only opposed the war, they did so vociferously).
The Three-Fifths Clause of the Constitution was ended by the Civil War, not by a vote or compromise or anything legislative. The Morrill Tariff was pushed through, as Lincoln promised, but to incredible cost that he clearly could not see beforehand.