Based on what I saw at Gettysburg, most (if not all) of these monuments were donated by citizens from states that had units at Gettysburg. Those statues are now property of the US Park Service, and help to tell the story of the most consequential, and bloodiest battle of the American Civil War.
IMO, Gettysburg is one of those moments that changed world history, just like the Trinity Site, Armstrong on the Moon, etc. This mad rush into sanitizing history must be stopped, yesterday.