[Non-Sequitur]

In other words, his real failure was in not ending slavery with diplomacy.

That's like saying the U.S. was at fault for not settling the fallout from the Pearl Harbor attack by diplomacy. The confederacy chose war. Lincoln fought the war that they forced on him.

[central_va]

The confederacy chose war.

If anyone chose war it was the "Goon" himself, read his second inaugural again, Para. 2.