It has nothing to do with why armies marched across the border to subdue them. It doesn't matter what the confederates put in that constitution, the armies would have still marched across the border to make them submit, and you know it, though you don't have the honesty to admit it.
Also the US Constitution enshrined the right to keep slaves. You keep wanting to ignore that fact, but Abraham Lincoln himself repeated this over and over again.
You have an emotional view that you *WANT* to be the truth, but it is not actually true.