I think you're missing the point. Those Confederate monuments were erected in the first place to uphold the ideal of white supremacy. A study was done showing that the building of those monuments spiked when there were increased pushes for civil rights for African-Americans. Those other things you mentioned are not the same, as they weren't created to celebrate the less savory aspect of those people's histories, whereas the Confederate crap was created with a view to celebrate when black people were oppressed and to intimidate them.
No one is suggesting to "sanitize" history, but rather not to have emblems on public land representing and celebrating the oppression and enslavement of African-Americans.
I keep posting this:
Confederate Statues Were Built To Further A 'White Supremacist Future'
You make some good points, although one thing I would note is that, coinciding with the years these monuments were built was also the promotion of the Lost Cause version of Civil War history, in which pro-Confederate historians were trying to pass off the idea that the Civil War was about anything
but slavery. The Northern states went along with this idea, too, for their own reasons. Grant was a big believer in reconciliation and patching up the nation's wounds. He and Longstreet became close friends after the war.
If generations were being born and raised to think that the Civil War was "not about slavery or white supremacy," then it seems odd or incongruous that there would be some kind of subtly cynical motive behind the construction of Confederate monuments. It seems more likely an attempt to confirm the overall Lost Cause version which maintained in telling the story of what the Civil War was
not about.
That is, if the monuments were constructed as a form of post-war losers' propaganda, then the whole idea would have been to try to make the Confederacy look good in the eyes of the public.
What's happening in more recent times regarding the push for tearing down these monuments and flags is not so much a demonization of the old Confederacy - which only lasted four years. It also calls into question as to why America, as a whole, tolerated these statues, monuments, and flags for well over a century after the end of the Civil War. Why did America, as a whole, continue with white supremacist policies for the same length of time? I don't see it as a matter of statues or monuments, nor is it even about a skewed version of Civil War history (although I don't see that replacing one skewed version with another helps clarify matters).
The problem with the way a lot of people study U.S. history is that many try to compartmentalize it into neat little packages, when the reality was a lot more complicated and messy. The history of the Confederacy has been woven into the overall tapestry of U.S. history as a whole.
I'm not saying they shouldn't tear down the Confederate monuments. They probably should have torn them down decades ago (or never allowed them to go up in the first place), but regardless, if we're doing it now because it's politically expedient and makes people feel good about themselves and their history, then I would suggest it's being done for the wrong reasons. It's the same line of thinking that brought about the Lost Cause version in the first place.