In what instance in history have two regions with such a shared history, bound by both revolution and a functioning republic, amicably separated?
As I said before, all laws come down to whether you can enforce them. There was never a chance for an amicable secession. To claim so is ridiculous.
So if you're claiming secession was legal, then great, but by about, ten minutes after the formation of the republic, the fate of the south to be numerically and technologically inferior to the north was already set in motion.
And so since a successful secession was very unlikely to begin with (see my post in another thread asking when the sweet spot for secession was), then the question "was it worth it?" becomes much more of a moral question for *EDITED*or, as we have seen, at least requires a considerable amount of mental and historical gymnastics to reconcile.