There's an old saying about those who don't learn history being doomed to repeat it. it's an old saying for a reason. Honestly, and this may sound harsh, but as you know, I see it from both sides being mixed race. My ancestors were stolen from Africa and wound up working on SC rice plantations. I have other ancestors that owned slaves. Anyway, back to my point, I think whitewashing occurs for a couple reasons, first, there's a lack of accountability., or a lack of willingness to be accountable. It's like there's a fear that if they teach it, recognize it and affirm the truth it's goign to take something out of their precious pocket or some nonsense. These are the folks like some of my relatives that say, "hey, it wasn't me, so what's the problem, I didn't have a slave."
Or, even worse, they don't see a problem with it. To be accountable, to teach the truth might disturb the current and prevailing power structure and goodness knows they don't want that. I could go on for days, but I'll leave it there. I very much enjoyed your story.