The Southern states reasons for leaving have nothing to do with the Northern States reasons for forcing them back in. Since the Northern States had control of the war, it was *THEIR* reasons that mattered in the conflict, not the Southern States reasons for wanting out of the Union.
The Northern states had no interest in stopping slavery when the war began. They only wanted to get those Southern states back under their control.
Despite the limited terms of the Emancipation Proclamation, it marked a decisive shift in the North's war aims, from simple preservation of the union to preservation plus the end of slavery.
Well see, there you go. Yes it did mark a decisive shift. It moved the goal posts to something other than what actually started the war. If the point of the North going to war wasn't to end slavery, then why do people keep repeating that it was?
If the South had instead remained in the union, they could have stymied abolition while undertaking gradual reforms that ameliorated the conditions of slavery. Doing so would have preserved the South's prosperity and political power.
On the other hand, had they simply been allowed to remain independent, they could have been even more prosperous anyways without having to listen to their Moral superiors in the North East telling them what horrible human beings they were.
Producing 3/4ths of all US Exports without New York taking a 40% cut out of their profits would have given them plenty of capital to build industries to rival the North. This I think was the real reason why the US went to war with them. There were plenty of Robber Barons with power and influence who would have lost both had the South remained independent of their control.
In contrast, it was illegal in most of the antebellum South to teach Blacks to read and write. Wary of the disruptive potential of industrialization for slavery, the South expressly looked to the agriculture and the cultivation of crops that were congenial to slavery. Expansion into Central America and the Caribbean were projected for additional slave crops, for territory, and for added strategic position and strength.
As it was, the horrors of combat and long casualty lists of the Civil War gradually drove Northern opinion toward emancipation. The scale of the sacrifice that the war demanded called for a greater purpose than saving the Union. With the victory at Gettysburg, Lincoln thus issued the Emancipation Proclamation and redefined the conflict.
Meanwhile, with even greater proportional casualties and the Confederate cause failing as the North's armies advanced, the South's leaders rejected freedom for their slaves even if it could secure Southern independence. Like all great conflicts, the Civil War wore its way through to fundamental causes and issues.
For all the romantic appeal of the Confederacy and of the Lost Cause myth, it should not be forgotten that slavery was wrong, wrong, wrong, and that secession and civil war were foolish and self-destructive. The better course is to recognize and accept this, while cherishing the South's genuine and considerable virtues and her contributions to America's greatness.
Notably, in the modern South, White Southerners' restraint and peaceful protests by Black Southerners against segregation provided a model for the rest of the world. Instead of revolutionary violence, the American South showed that peaceful protest and generational change could redress deep grievances.
Southerners also provide much of the core strength of the American military and an attachment to traditional manners and virtues. The grandson of immigrants, there are no Confederates in my ancestry, but I would not willingly live anywhere but the South.