Built into this is the assumption that violence need follow separation. There are examples of peaceful secession, though not many.
Can you name an instance of peaceful secession where one party acted in a unilateral manner? Without the agreement of both parties then you are guaranteeing conflict.
It's beside the point. The point is that if the Congress has the right to set tariffs, then they are not acting unconstitutionally. Therefore, all the states are obligated to adhere to them, or use the proper channels to alter the law. To resist the lawful execution of national policy is to invite enforcement, which is to say, violence.
For something called "secession" to occur with any hope of peace, all the parties to the compact would have had to agree to it, or at least to agree to a process from which it would be decided. That wasn't the case.
You can't undo the Constitution--or your obligation to it--just because you don't agree with policy, or the outcome of an election. That's anti-republican. It's anarchy.