I'm not sure you actually disagree with Mr. Hess? You can teach the reality of the stark contrast between the lofty ideals promulgated by the Founding Fathers and the repulsive exploitation that some of them actually engaged in without, for example, making a kid whose parents immigrated from Ukraine in the 90s feel like he's a bad person just because of his skin color.

Just tell the parent: No, teaching how things actually were is essential for understanding how things have improved. And it's important as a warning to keep alert for problems today so that those too can be improved in the future.

How you can get anything but good out of that, I don't know.