Well, I have two degrees in history, including an MSE, so I've spent a great deal of time studying that particular era.
If you're going to debate the causes of the Civil War, you're going to have to give up the attempts to seize the moral high ground.
The secession crisis of 1861 was not an insurrection in its inception. The Deep South states withdrew in a peaceful, if somewhat uncertain and cautious manner. Negotiations were underway from the beginning between Lincoln and the newly formed CSA government, to prevent bloodshed. Lincoln certainly hoped to persuade these states to return peacefully to the union. Most leaders on both sides of the issue wanted to avoid violence. However, there were, of course, hot-heads on both sides who wanted war. Unfortunately, some of these controlled the batteries aimed at Fort Sumter.
What might have happened if those batteries had not precipitated that conflict is one of the great unanswered questions of our history. Would Lincoln have invaded the South if that was the case? Would the Southern States have been permitted to leave the Union peacefully? Since the states entered into the Union voluntarily, would their "right" to leave voluntarily be recognized by the Federal government?
The entire argument over secession and states' rights would have had to have been settled with debate and negotiation, rather than by force-of-arms, which is the worst method for settling ideological questions of this nature.
