For Republicans and abolitionists, freedom had a pretty simple definition. Men don’t owe their labour to anyone else. They believed in the phrase “All men are created equal applied to blacks as well”

For Southerners, as the years progressed, they became more financially entangled in the institution of slavery and thus spent enormous effort and mental gymnastics to justify slavery: God wants slavery. Freedmen in the North are slaves to industrialists whereas even the poorest of whites in the South didn’t have to do negro work. Southerners couldn’t economically survive without slavery. Slavery protects whites women from black brutes...

Of course many Southerners saw through the propaganda and were loyal to the Union and were anti-slavery.

But for most of the South, slavery was a massive portion of the culture and the economy. The South was a slave culture and a slave economy before all else.

Around the topic of “States Rights” and the freedom and liberty of States, that was all about slavery. It was also known as “Popular Sovereignty”. Stephen Douglas was one of the biggest advocates of it and the general idea was that slavery wasn’t a moral question. It should be democratically decided inside each State. Even in Northern ones where it was previously banned. This was the political method by which slavery could spread in to new States. It led directly to war with Bleeding Kansas. Ultimately “States Rights” became a battle cry for white Southerners to fight Northerners. They needed something like that to rally their men. Men can be made to fight for freedom and defence. Not only to protect the slave assets of plantation owners. It had to be an indirect plea.

The book “Battle Cry of Freedom” is a highly respected book about the Civil War. And that title alone signifies the importance of the question you asked. I believe that book covered everything I wrote above but I may have mixed in something from other sources as well.

More of course can be said, but I imagine you'll find this to be of interest.