My argument was from the Christian principles regulating Just War. Much of this can be found (is it still there?) in the UCMJ. Nor do I think Yankee soldiers were all depraved war dogs,and CSA'ers were all Marse Robert.
If, as you say the rate of civilian casualties was much power in the U.S. Civil War than in other civil was, then I give credit to soldiers and officers who were just.
Related: the mass die-off of black slaves--- hundreds of thousands of them --- as a (surely unintended) consequence of the Civil War and its aftermath.
I've never seen that subject addressed directly, and would be most interested in a reasonably-short summary.
But have long suspected that when people throw out numbers like "50,000 civilians died", since there are no actual records, then if there's any reality to that number, it may refer almost entirely to rough estimates of slaves who died from economic & social disruptions of the war.