States pass laws all the time that the fed later contradicts. 99.9% of the time, the state deems the issue of insufficient consequence to drive a break with the federal government. Occasionally an issue arises (once, so far) that the states cannot or will not compromise on. When that happens, they may choose to secede. That was what happened in the civil war. They didnt do it to prove a point, that they could secede. The did it because the issue of slavery was one on which there was no further compromise. So yes, it was fought over the right to secede but why did those Southern states secede? Slavery. You just can’t get past that part.
What you don't understand is that slavery was the occasion; states rights was the cause.
Can you answer the question in my hypothetical secession case?