Well written post. I wish I could explain today, but I cannot :(

I agree here as well "humankind learns as it becomes more enlightened, and we don't accept these acts of human cruelty any more" but that then supports leaving monuments alone, or moving them, not destroying them.

As for the KKK activists, in the scenario that occurred, they were simply gathered to protect the statue of Robert E. Lee, and in that single case, I agree with them-not the counter protesters  actions which toppled and destroyed it. But I cannot explain that either. We see that destruction of statues with ISIS when they claim a location, but I never thought we would see it in America. Sadly, I was wrong.

To close: 
You ask: If the Confederacy had actually won the Civil War, what do you think would have happened to the black slaves who couldn't escape?

I think that life would have continued, and very sadly, the slaves would be owned as they were.  For it was the Dems (at that time) who fought slaves freedom.