Again, if I was going to threaten $700 million in Northern trade and income, I would certainly point to something else to misdirect what I am really doing.
But you keep focusing on the South's alleged reason (as if you have to justify a right to independence) than you are on the actual real point of this discussion, which is the North's reason for invading them.
The North should be on the defensive here. The South had a right to leave, and the North had no right to stop them.
Why did the North invade them? It clearly wasn't because of slavery.
Long before John Brown, the Denmark Vesey conspiracy and Nat Turner's rebellion demonstrated that violent slave revolts were a tangible risk. In addition, poisoning and violent assaults by slaves were feared by the South's slaveholders. John Brown's attack at Harper's Ferry hit a raw nerve.
From what I have read on the topic, they were always afraid of the possibility the slaves would revolt. They had allowed them to become so numerous that they then feared them as a threat.
And of course the North wouldn't punish anyone for sending the John Brown raid. It's just like the Liberal states with ANTIFA or BLM.
Consider that the Declaration urges that "a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation." Yet you insist that while slavery is prominently mentioned in the official Southern statements of secession, economics was the real reason. If you are accurate, that obscurity takes Southern secession away from the requirement of the Declaration that the causes be stated.
Moreover, the Declaration states that "all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness." This principle makes slavery ineligible as a legitimate basis for secession.
As for whether the North had a right to oppose secession, the Declaration did not claim that Britain had no right to try to keep America as a colony. So why do you insist that the North had no right to try to preserve the Union?