Do you want to know the truth, or do you just want to see a bunch of teeth-gnashing?!The truth, which neither side ever accepted, was that:
1. The North was morally right (e.g. slavery was unethical) and militarily right (e.g. might makes right, a united America is better able to deal with European/Asian troubles, et al),
and
2. The South was legally right. The 9th and 10th Amendments to the U.S. Constitution reserve the right to secede to the states. Slavery was likewise ruled legal by the U.S. Supreme Court in the infamous Dred Scott decision.
Thus, both sides marched headlong into war "knowing" that they were right and that their brothers were wrong; a dispute that sometimes still smolders even to this very day.
In fact, Leftists like to dredge up the issue in their many attempts to further divide America. They love to paint slavery and Confederate imagery as grossly evil on the one hand, and on the other hand they love to show the South in a sympathetic light (especially that the South was noble but "wronged") in their articles, books, and movies.
But they don't do so because they think that the South was right. No, they do so in the hopes to further drive a wedge between various Conservatives (North and South, Black and White) in America.
To the Lefties, the more that they can bring up this national wound, the better (as many useful idiots will jump on board various bandwagons to add yet more salt to the old wounds)...