The fact that thousands of men on both sides died, to end a problem that would have eventually been solved peacefully, is not a blessing.
Hindsight is 20/20. When the South went to war to protect their institution I've no doubt that they all thought slavery would continue for generations.
This problem was not going to end peacefully and you have no evidence that it would have.
The new Confederate Constitution wrote Negro slavery into it as a right.
It was the South who not allow it to die peacefully, since all Lincoln wanted to do was restrict its growth and spread.
But some evils have to be eliminated with force like Nazism and Islamic facism.