How are you not convinced when many of the states in their reason for leaving the Union claim slavery was the cause? Many Confederate soldiers diaries said the same.

There may have been side excuses such as states rights or state sovereignty but the Fire Eaters such as Robert Barnwell Rhett clearly stated their reasoning for pushing for secession.

This stuff is just too easy for folks to claim they are not convinced or do not know. How about this quote by Rhett one of the authors of Southern secession:

"Independent ourselves, we disclaim any design or desire, to lead the counsels of the other Southern States. Providence has cast our lot together, by extending over us an identity of pursuits, interests and institutions. South Carolina, desires no destiny, separate from yours. To be one of a great Slaveholding Confederacy, stretching its arms over a territory larger than any power in Europe possesses–with a population, four times greater than that of the whole United States"

Or how about the end of his same speech:

"We ask you to join us, in forming a Confederacy of Slaveholding States."

Every American should be required to read Rhett's writing and speeches. He rightfully damns the North, business interest and Constitution as being founded on slavery, he the vile old white supremacist never wavered in his support for owning humans beings.