Explanation: The US Civil War was kicked off in 1861 after the election of the antislavery candidate Abraham Lincoln in late 1860. The radical antislavery position Lincoln held?
... that slavery shouldn't be allowed to expand outside of the South.
Not "Slavery must be immediately destroyed by the Federal government". Not even "Slavery in the South must be reduced by the Federal government." Just "No expansion."
Obviously, to the slaver cunts, this was unacceptable oppression, and they then attempted to secede after losing said democratic election.