It is ironic that the exact same people that formed the Klan, also formed BLM; for the same purpose...to destroy them! It is also disappointing when a people blindly become, that which the hated....
My ancestors were part of that effort, and they were Constitutionally wrong. Every state had the right to peacefully leave the union. The freeing of the slaves was added as an afterthought. The institution of slavery was actually doomed by farm automation anyway, when machines became less expensive to use!
So even without the Civil War, the slaves would be free, and the CSA and the USA would be tied together by compatible economies.