Celebrating the confederacy is wrong, but I also think museum-like stuff and graveyards are harmless and should be respected. First of all, not everyone who served had much of a choice. Many were expected to serve on one side or the other merely because of where they lived. This is true of much of history. Second, they're dead. It's over for these specific people. They're not a current problem. It's just disrespectful no matter who it is.
I am NOT defending anything confederate, but I know that nuance is lost on most people.