Take slavery. Slavery, and its by-products including lynchings, breaking up of families, and the subsequent marginalization and disenfranchisements of those people, exists in the U.S. to this day. The interests of jurisdictions that want to deny such knowledge are ostensibly concerned that people learning of these things, things that their ancestors participated wholeheartedly in, may cause a mental meltdown. After all, how do you reconcile something like people who regularly attended church and who show they believe in Christ almighty and his teachings, yet have undertaken in things like slavery et al., disregarding things like loving your neighbor as yourself, loving a stranger among you as you love yourself, and recognizing that those who love God, no matter who they are, are entitled to the same inheritance of Abraham, being heirs according to the Promise to Abraham that God made?
In a sense, such a fear of a mental meltdown goes against human nature. It is more likely that an individual who is presented with conflicting knowledge will undertake every effort to reconcile the conflicts to see if there is an explanation they can live with. In most cases, people who are faced with such cognitive dissonance, especially when it involves people they love, will resolve it to their understanding. This is one way that one acquires wisdom. In accordance with Verses such as Proverbs 1:7, God wants us to acquire such wisdom. But to know wisdom is to know good and evil...and if we hide our heads in the sand to avoid learning of the evil that is in this world, we will not have the capacity to exercise wisdom.