The violence came because the seven states that had seceded thought that if it came to war, some of the slave-owning states that had not seceded might join them.
They had the choice, between peacefully seceding as a Confederacy of seven states, or starting a war and perhaps becoming a Confederacy of eleven or thirteen states.
They chose war.
I agree, the North chose war over letting the South go her own way, Yankee bloody fascists.