I think it's a little bit revisionist and Lost Causeresque to hang your Confederate sympathies hat on the legal/constitutional peg. When you think you have a point worth dying for you put your gonads on the line and go for it. You wake up and say, "I'm going to go out and rebel today, it's going to be illegal, and if you don't like it you're going to have to stop me. Now bring it."
Well, they did. If you are going to secede, you better succeed.
I have a hard time getting my mind wrapped around why some with Confederate sympathies think it's important to argue that secession was legal or constitutional. Again, if it was that's fine. But if it wasn't isn't that fine too?
I have to agree. By the act of secession you are breaking the bonds of the laws of the government, parent corporation or political organization. In the act of secession the laws no longer bind you. You are making all their laws null and void. The problem is with that separation you invite them to force you to stay if it is in their financial interests to keep you. The South owed too much money to the Northern bankers and investors to simply let them go. The fear of the secession was the South would default on nearly $1 billion dollars in Northern loans. Let alone the lopsided amount of taxes paid by the South and incredibly small return they were getting. Secession also invites an open and free competition in the markets not constrained by the Northern parent government. Lots of financial ties in jeopardy with the Southern Succession.
Secession is not about rights but about finances. It is of course very flowery to discuss it in terms of rights but that simply is not the way the world works.