The People decided for Union in 1776. The People ratified the Constitution of 1787. They made their decision, and that was for a perpetual, constitutional Union. Once they did so, they were bound by the laws of the government they formed. No state had the authority to unilaterally remove itself from the Union. The states did not possess the sovereignty to do so.
There is nobody I've ever met in my life who was more wilfully and boneheadedly wrong about anything, ever.
Yes, they damn well did.