I disagree with your speculation, you can't wipe away the sinful cause of the Confederates with "if there hadn't been slavery" because they fought to defend the institution. Sometimes the fight between good and evil actually manifests itself physically.
All the reasons that the ConfedeRATS made up for secession were attempts to excuse and cover up their hideous disregard and abuse of the freedom of others, while incredibly claiming to be fighting for freedom themselves!
You couldn't be more wrong. Except for a few New England abolitionists, no one, NO ONE in the North was fighting against slavery.