All of my ancestors arrived in the USA in the 20th century, so I don’t have any emotional relationship with the Confederate flag, monuments, statues, etc, but I do understand their integral part in our history. Just as “hot” is a concept without “cold” or “wet” without “dry”, the “United States” is meaningless without the various antitheses which comprised its founding. The United States, a plural word before the Civil War, fused disparate, even contrary, elements in an alliance of convenience against a common foe, Great Britain, until those contradictions become intractable only the largest war ever fought in the Western Hemisphere could resolve them. Some small fringe of Confederate flag adherents, use it as a racist hate symbol, but to the vast majority it simplifies other things - family/ancestral heritage, rebellion against central authority, local anatomy, hierarchical rather than (Marsian) egalitarianism, social order, resistance to abuse of power, etc. It is an enduring symbol precisely because it is so multi-faceted.
Those who would remove these confederate symbols are closer than they might imagine to the Islamic State bulldozing Nineveh's and Palmyra’s ancient ruins as “pagans.” Both believe these things must go because they are morally offensive.
But the proverb reminds us to “remove not the ancient landmark thy ancestors have set” precisely because we need to understand our history. If what our ancestors believed was important we find offensive, we still need to be reminded of it, if only so we know not to go that way in our own historic development. If we airbrush Alexandria’s Confederate past, it will be largely lost to future generations. Those who forget the lessons of history are doomed to repeat the same mistakes.