If you want to reduce the Constitution to a mere contract then I'll play along. Contracts are binding on both sides, and one side can no more void the contract unilaterally than the other side can. If one side believes the other side to be in violation then the contact allows for means of mediation. Walking out on the contract is as much a violation as anything else.
Do you think South Carolina was in any way justified writing its declaration of secession?
South Carolina needed no approval from me before writing their declaration. I would say, however, that most of their complaints were inaccurate or unjustified.
But South Carolina claimed it was not getting any mediation, only 25 years of being hassled.
"Walking out on the contract is as much a violation as anything else."
Exactly what South Carolina accused the northern states and federal government of doing when the government refused to protect what everyone agreed to be private property at the time the supreme law was written.