And elements in the South absolutely despised the North. Wealthy Charlestonians certainly felt justified in talking down to New Yorkers. Why don't you do a little reading. Here's as good a place as any to start: Madness Rules the Hour: Charleston, 1860 and the Mania for War.
One of your comedy gems was saying that Chicagoans were elitists who looked down on the South. Chicago had been a tiny village -- pretty much a swamp -- thirty years before. They weren't snobbishly looking down on Richmond or Charleston or New Orleans. It was the other way around.
Another hilarious thing you wrote:
According to the North, Slavery wasn't under any threat, so your claim doesn't even make sense on the face of it.
On the contrary, it's your denial that makes no sense. Republicans said they weren't threatening slavery where it already existed, but the slave owners didn't believe them. They felt that any admission that slavery was wrong or morally questionable weakened their economy and society to the breaking point. For some Southerners the fact that the government wouldn't be in favor the expansion of slave territory was enough of a threat or an insult to justify secession.
Your point only makes sense if we conclude that the Northerners didn't believe them. It was obvious that the Southerners didn't believe them, but if they were going to keep their word, slavery would have remained in the United States for much longer than it did.
They felt that any admission that slavery was wrong or morally questionable weakened their economy and society to the breaking point. For some Southerners the fact that the government wouldn't be in favor the expansion of slave territory was enough of a threat or an insult to justify secession.
It was more than just their desire to believe Slavery was morally correct, there was real political power attached to this. Slave states could be counted on to vote as a coalition regarding matters beyond just slavery. The Southern states wanted newly added states to vote along with the Southern states in congress, and they believed that this would happen naturally if those states became slave states. So too did the Northern states believe this, and that is exactly why they didn't want slavery in the new states. They wanted to keep the political power that they had finally obtained.
Each side wanted the new states to side with them politically in Washington, and I dare say none of them gave a crap about the actual slaves themselves. The slaves were merely pawns in a larger game of political power.
This is one of the reasons that Southern independence was a grave threat to the political and financial interests of the North East. If the South seceded successfully, they could eventually buy influence in the new states and get them to join the Confederacy. They could have supplied goods and services to the entire area by way of the Mississippi.
They would not only take those markets away from the New York coalition, they would gain those lands and that future population. The Confederacy may have eventually grown to be the larger of the two countries, and that just couldn't be allowed by those who had the controlling interests of the Northern one.