War was declared by the South. The first military action was taken by the South. If you believe in the U.S. and its founding principles then you should have no difficulty seeing the North was in the right and the South was a degenerate aristocratic oligarchy.
No one is glad they fought the war, but I am glad the North won. The battle flag has its place as a historic object, and of course individuals should be able to display it if they want. But no state and certainly the Federal government should have nothing to do with it beyond teaching the history in public schools.
The fact of slaveholding by Southerners was really only one facet of the differences between the North and South, and claims that Northerners profited from the slave trade before importation was banned are of course valid.
But when it comes down to it there was a war, the winners were very fortunately the ones who were ultimately against slavery and in favor of liberty that isn’t based on property ownership – the South was big on stratifying social rights according to economic power.