I don't see how anyone can understand much about the war, secession, or slavery without taking a serious look at the role of religion. A large percentage of Southern preachers (I don't know any way to pin down a number) spoke regularly and enthusiastically about the supremacy of the white race being a core concept of Christianity in their view, which made slavery seem much more tolerable to many, including political leaders. Some ministers in fact actually argued that God had given the white man the responsibility for looking after black people and supervising them, since they allegedly didn't have sense enough to handle freedom. While this was going on, plenty of Northern churches were preaching that slavery was a sin and a moral outrage. Most Protestant denominations ended up splitting north-south over the issue.
The KKK claimed to be built on a religious foundation, claiming to be following the Bible's teachings on separation of the races, and some unsubstantiated claims pertaining to the skin color of various individuals mentioned in Old Testament stories.
And then there's the role of the pacifist denominations in influencing / delaying succession votes. There were enough Quaker and Moravian votes in NC to help swing close votes in the legislature, for a while.
While opinions may vary on the moral and religious merits of various things that were being taught, it is historical fact that such things went on, and played a major role in the period. Sermon transcripts have survived, documents pertaining to denominational splits have survived, and we have legislative voting results broken down by county and district, with known demographics. Politicians spoke and wrote on the morality of slavery using language that closely matched what was being commonly said in whichever denomination of church they regularly attended and had their membership. The influence is hard to miss.
Pull out the thread of religion, and the whole fabric of the Civil War story starts to unravel. It is woven through everything.