Would we object to a statute of a Nazi who didn’t support the holocaust (especially if he ended up being executed by the Nazi government)? What if he was merely not involved with the holocaust.
Do we object to statutes in honor of former American enemies with whom we now wish to be friends (e.g. Sitting Bull, Nat Turner)?
An argument can be made the rebellion of the American South in 1861-1865 was not initially about slavery but about the objections of the southerners to a modern, industrial society. Only some of the states that still had slavery (most states having abolished slavery in the aftermath of the Revolution) joined the rebellion, and most southerners were not slaveowners. Before the Civil War most Americans had never seen a Black person, and no one demanded that the south give up slavery in 1861, and the pro-union slave states were exempted from the emancipation proclamation. By the end of the war the Union was anti-slavery, and by 1865 most non-southern Americans felt they had been abolitionists all along, just like most Americans and Brits couldn’t care less about anti-Semitism in 1939, but by 1945 felt they had opposed anti-Semitism all along. In both cases, discovering the barbarity of the enemy (of slavery, and of the holocaust), combined with the struggles of war, changed minds