Their seeing themselves that way was an interpretation, a part of their world view, and as such may have led to misguided actions on their part. But interpretations do not have factual content and thus cannot be characterized as false. A quibble, perhaps, but I feel a need sometimes to state my objection to what I see as an gratuitous and inappropriate use of perjoratives, among which I would include your use of "over rationalistic".
I'd also like to make this clarification. As clear as it should be from my posts and explicit statements to this effect: I am a supporter of a very general right to unilateral right to secession and in particular in the case of the Confederacy in 1861. I am not by any means an apologist for the Confederacy in general or any particular personalities thereof. I hope you can understand this point; some (I won't mention names) seem unable to.
Okay, then I'd say that the comparison the secessionists made of themselves to the men of 1776 was an inappropriate or terribly incomplete analogy.
I am a supporter of a very general right to unilateral right to secession and in particular in the case of the Confederacy in 1861. I am not by any means an apologist for the Confederacy in general or any particular personalities thereof.
Okay again, but the idea of unilateral secession, which is not found in the Constitution, is a serpent's tooth that caused much trouble in 1861. Pursued as the men of 1861 did, unilateral secession couldn't help but make serious problems and increase the likelihood of war. For the reasons I've given in my previous post, I believe these troubles were inherent in the idea of secession on demand. That doesn't mean that the union was indissoluble, just that the country as a whole would have to have a say in the process of secession or dissolution.
Constitutional processes are shock absorbers that calm passions, encourage compromise, and put energies to constructive use. Theories of unilateral secession and absolute state sovereignty have the opposite effect, encouraging haste, thoughtlessness and hotheadedness.
I don't think that secession falls in the same category as absolute individual rights to free speech or freedom of the press or freedom of religion. I suspect the question is closer to contract or marriage law, where both rights and responsibilities are involved, and opting out one-sidedly counts as desertion or breach of contract.