That is hardly an accurate representation of the majority opinion. The opinion was based on the extra-Constitutional doctrine of the perpetual and indissoluble nature of the federal union which was in turn based on the absurd Lincolnian dogma that the federal union preceded the Constitution and was older than the states. Whatever the standing of the decision, its foundation is crap.
That's a new one on me. I've read the entire Constitution front to back and I haven't found where it says that the Preamble can't be used to form the basis for the court's decision. You've shown that you can make up new paramaters for guiding Supreme Court decisions, and you've shown where you do not disagree with Texas v. White, but you haven't shown where the decision is invalid or illegal and you havent shown where anything has come along to overrule or modify the decision. And unless you can then the simple fact of the matter is that unilateral secession as practiced by Texas in particular and the southern states in general was illegal.