There had to be some "justification" for the killing and maiming of two million, "ending slavery" happened to sound the more "noble" while the red man perished under those same guns. Funny how arrogance of moral value seems to stick us in our own backs sometimes.
How to win a war? Remove the enemy's production engine and they'll die. Slavery was the South's production engine, without doubt, no contesting that. BUT it was a Northern STRATEGIC decision to free slaves and diminish the South's ability to resist - by far moreso than it was a morally higher calling of the North to do so. The "Union" proved itself not so moral in the treatment of the red man after it's "battle of morality" inflicted on those bad slave-holding states.
This may be getting more off-topic, but highly interesting that members of the Cherokee Nation (REAL Indians, not fake 1/16th-Indian white guys) come to the Pt. Lookout POW memorial services to lay wreaths at the memorial to rebel POWs. I've seen it myself. The people were real, too, not just fakirs like the casino people up in Connecticut.