There are many things that the Constitution is silent on, but lawmakers have created law to govern and courts have ruled upon and affirmed. Reducing the argument down to bumper sticker slogans only serves to fog the truth. Here is a link to the Texas v. White case should you care to read about the ruing in its entirety: https://www.law.cornell.edu/supremecourt/text/74/700
As with all lawsuits there are predicates and contexts that need to be observed and considered if one wants to understand why a case was adjudicated the was it was.
As I’m sure you know, the case wasn’t about Texas’s right of secession - at least not initially. But Standing, Authority, and Sovereignty became elements. Here’s what the court said about the formation of the republic:
99
The Union of the States never was a purely artificial and arbitrary relation. It began among the Colonies, and grew out of common origin, mutual sympathies, kindred principles, similar interests, and geographical relations. It was confirmed and strengthened by the necessities of war, and received definite form, and character, and sanction from the Articles of Confederation. By these the Union was solemnly declared to ‘be perpetual.’ And when these Articles were found to be inadequate to the exigencies of the country, the Constitution was ordained ‘to form a more perfect Union.’ It is difficult to convey the idea of indissoluble unity more clearly than by these words. What can be indissoluble if a perpetual Union, made more perfect, is not?
Jumping ahead, the ruling states:
101
When, therefore, Texas became one of the United States, she entered into an indissoluble relation. All the obligations of perpetual union, and all the guaranties of republican government in the Union, attached at once to the State. The act which consummated her admission into the Union was something more than a compact; it was the incorporation of a new member into the political body. And it was final. The union between Texas and the other States was as complete, as perpetual, and as indissoluble as the union between the original States. There was no place for reconsideration, or revocation, except through revolution, or through consent of the States.
That last sentence is the money quote. SCOTUS doesn’t recognize secession as a constitutional act unless done with mutual consent.
BTW, notice this exercise in doublethink:
"By these the Union was solemnly declared to ‘be perpetual.’ And when these Articles were found to be inadequate to the exigencies of the country, the Constitution was ordained ‘to form a more perfect Union.’ "
LOL. This constitution must be perpetual, even though it doesn't say it is, because the last constitution said it was perpetual, even though it wasn't.
Look all you've done is demonstrate that SCOTUS ruled secession unconstitutional. That was not in dispute. The point is that the court ruled something unconstitutional that the constitution is silent about. That remains a contradiction.