If perception were reality, conspicuous consumption would make you rich.
Lies can affect peoples' actions, but cannot change the underlying reality. You can ignore reality, but not the consequences of ignoring it. So we get to Karl's point that if we fail history we are doomed to repeat it.
I just recently went over this point about the actual causes of the war of northern aggression with with my middle child, who is now in high school. She is not a scholar, so I wound up getting her a little pamphlet titled A Confederate Catechism. It did a pretty good job of laying out the issues we've seen in this thread, at a level an intelligent but incurious teen can access. My oldest is more scholarly, and has read some of the original sources, but the English of 1840 through 1880 isn't accessible to most Americans today.