Perhaps the more important lesson here is the way that Americans want their history. We won’t tolerate any sin or injustice (don’t think the Old Testament). Mix any sordid parts of human exploitation in and you better close down the museum or rename the holiday. In other words, deep down Americans all want a Chamber of Commerce version of history. The right thinks of America as only great all the time. The left wants greatness but can’t handle anything less.
But related and not without significance is apologist’s argument that uses on history to vindicate a specific Christian communion. If you bring up the past, be prepared for the boomerang.
No cherry picking.
As Hart would know by now having written a chapter called something like "The Search for a Useful History" cherry-picking a history based on ideological commitments in the here and now for an ideal future is the American way. :)