I personally don’t care much about monuments unless they happen also to be great art as statues. Most are not. If taking down some monuments helps heal the wounds in the USA, I’m all for it. However, this statement of yours seems to run counter to actual history:

“What’s more, there is no instance I know of where a nation’s raison d’etre for war was to preserve the institution of slavery.”

The nation that won war went to war to end slavery. Surely your statement should read, “What’s more, there is no instance I know of where a nation’s raison d’etre for war was to end the institution of slavery.”

You are not helping matters by turning the purpose of the civil war upside down.

The war to end slavery was won by the North. At the moment of that victory, the entire nation was remade and became defined by this victory. Slavery was ended. The southern region of this remade nation dragged its feet and tried to get around the consequences of defeat. Today the USA is still trying to fully grasp this fact, this victory of and for civilization. Every remaining vestige of slavery and the racism that characterized it is being pulled out into the light and toppled. And one day, this too will be ancient history.