@joefromchicago,
First you should be aware that in the early 1960's NYC high schools taught that slavery was NOT the cause of the Civil War. Could that have been because the dirty little secret is that those in educational management knew that in a few years Northerners and Southerners were going to be fighting in Vietnam, and there was no reason to exacerbate regional differences?
Second, I do not think that before the Civil War the North was threatening Southern states to end their slavery; however, that makes me think the real point of contention is whether the western territories were going to be free or not. And, as I've read, that was why Northern men joined the Union Army - to make for a "white west," where white males could find employment outside of the insular slave plantation system.
But, this argument seems to be focussed on just historical facts, not what motivated them. I am just concerned that to accept slavery one was part of a majority in the South that had a very different concept of morality. Or, as I've read, at that point in history, Blacks were not considered equal to whites, similar to the dichotomy that the Third Reich promulgated about Jews in Europe. So while many talk of the Holocaust, few want to delve into what allowed Germans to consider Jews lower creatures that could be exterminated.
So, we really do not have an argument. In my opinion, few want to question what drove the morality of the slave owning South. Without understanding that, history may be quite sterile, and doesn't offend.
My point was shown in a PBS documentary explaining that the Northern abolitionists, who mostly were Evangelical ministers, believed that like instantaneous epiphanies of the unbeliever, the Southern slaveholder could have an epiphany of the immorality of slavery, if he was only educated. So the abolitionists wrote, and mailed, to Southern plantation owners, "tracts" that explained the immorality of slavery. It was met with the hostility one meets when one hits a bee hive, so to speak. So, there was a difference between the North and South. While white Northerners were not like the Northern liberal of today, he did not believe in slavery.
If you do not like my opinion, that is why I am lucky to be born in the U.S.A. . I am entitled to my opinion. And, you to yours.