we ‘shouldn’t’ try to hide the bad things we’ve done when we teach history
The keyword here is shouldn’t. Most people don’t do lots of things they should.
Not out of malice but simply laziness, it is a lot easier to just default to the norm and go on. Try comparing what should get done in politics(campaign promises) to what actually gets done in washington. In short what should happen and what actually happens are two different things in a lot of areas.