The Biggest Cause of the Civil War was Slavery

I Quote from Article 4 section 3 of the confederate constitution,

I Quote from Confederate Vice President Alexander Stephens in his cornerstone address,

 These quotes aren't the entirety of my argument, but they demonstrate the point I'm trying to make. Many confederate leaders openly said the war was about slavery. 

To step back a bit, let's trace the cause of the war back from its first shots at fort Sumter.[1] For a brief recap, after southern secession, the union still held on to a lot of federal forts in the south. At Sumter, Robert Anderson refused to give up the fort and was forced to cede it after a short artillery barrage from the confederates marking the first shots of the war. Lincoln is then forced to declare war.

Now let's follow this train of events back to its heart. Lincoln declares war because the confederates shot on fort Sumter, because the Confederates didn't want the Union having a military presence in their territory, because they wanted their sovereignty and separation from the union, because they wanted the right to practice slavery.  Now I recognize that in the early days of the war, Lincoln's true motivation was keeping the union together, and the emancipation proclamation was a strategic war time move, but while it can be disputed, I believe the confederates were the aggressor. Think about it this way, if the north had changed their actions, the war may have been prevented, but if the south had changed course the war would have 100% been avoided. In that case, the only motives we really need to take into account are the motives of the aggressor, which are slavery.

Is it really a coincidence that every seceding state practiced slavery? Is it really a coincidence that the south seceded when a president was elected who was supposedly going to take their slaves? Is it really a coincidence that the civil war was at the head of decades of culmination about the issue of slavery?

The states rights issue had come up before, but those incidents had almost nothing to to with the civil war. In this specific event, the state right in question was slavery, and almost nothing else. If other rights were in question, they were minimal at most. You can see this by the fact that all the states broke away all practiced slavery. It’s improbable that it’s just a coincidence that all states of the confederacy had slavery. 

While other issues were at play, slavery was the biggest one. States rights conflicts before were along different geographical lines, and had nothing to do with this specific conflict.

To close, I'd like to half-make a joke, and half offer a real question. Whenever I hear someone say that the civil war was about state rights, my automatic response is "A states right to do what?". So that's my question to you. If you choose to go the "states rights" route with your argument, what was the specific state right in question?