Professor Jay explains that the War Between the States was as much a theological crisis as it was political. The "culture war" between the conservative Christian South and the religiously liberal North centered on the South's literal view of scripture and the North's abandonment of the fundamental doctrines of the inspiration, preservation, and authority of scripture. This translated into politics as southerners still interpreted the constitution literally whereas northerners like Lincoln and his fellow Republicans saw it as a fluid and "changing" document.
Congress was debating a "civil war" decades before States began to secede. Also, slavery was not at issue in most of that debate but it did become an issue toward the end so the author lays out the cases for and against the institution that were made in religious institutions both North and South.
Also asked is the question of if those who erected our now controversial Confederate monuments did so for "racist" reasons why didn't they just declare it on the monument pedestals? Could it be, that as the pedestals declare, the Southerners did NOT have racist motives? Maybe their intent was clear in their writing - just as the intent of scripture was clear - and the intent of the founders in the Constitution. In other words, the yankees of our day are twisting the intent of our ancestors just as they twisted the intent of their own ancestors.