I'd like to raise an educators' paradox, and it goes as following: that there will always be motive to promote certain ideas in such a way that, in the long term, undermines support for such.
Let's take the most dramatic example: a historical government which we'll called Mustachestan (because I have no faith in the current lineup of mods to not sperg out at the use of a word in an innocuous context) is known to have committed mass murder. We know this to be a straightforward fact; there's mountains and mountains of evidence to support that this really happened. With me so far? Good.
Now, if some uninformed or disingenuous person claimed that Mustachestan did not commit mass murder, hearing this claim wouldn't cause a regular person cognitive dissonance, because, rather than taking belief in the fact of Mustachestan's crimes for a marker of personal identity, a normal person merely responds to what he or she knows to be the truth, and hearing a very dubious claim from a possibly dubious source won't suffice to persuade them toward falsehood. Likewise, one may feel viscerally powerful emotions like grief, disgust, or rage at learning of (or later reflecting upon) the enormity of Mustachestan's crimes, but they feel said emotions because said crimes happened; in other words, knowing how to react to Mustachestan is a posteriori, not a priori, knowledge; one would not normally feel these emotions in the face of atrocities that they were not aware of, or in an alternate reality where said atrocities never occurred.
Where am I going with this? If an educator believes that it's important, for the sake of preventing any regime like Mustachestan from ever rising again, that the next generation understands Mustachestan to be evil, then it's incumbent upon him or her to teach them why Mustachestan is evil. In other words, he or she ought to instill an evidence-based education on the topic. Photos of dead bodies and liberated death camps, testimonies of survivors, and so on. Since the evidence overwhelmingly supports the fact that Mustachestan did evil deeds on a scale that only a truly evil government would do, and had no justification compelling enough to excuse crimes of said magnitude, an evidence-based education would serve to convince the overwhelming majority of people.
I don't think I've said anything remarkable so far, but there is a point to this, I promise.
What I described above is the ideal. But my hypothesis is that some educators are uninterested in this approach, and they fall into two camps.
First, there's reasonable people who would raise a counterargument to the above: that some crafty people will devise superficially convincing talking points whose refutation might entail some difficulty, especially in a relentless bullet point format that educators can't keep up with. Most people have enough of a head on their shoulders to not buy into this, but a few gullible people might, and it'll give a few stubborn people excuse to not ditch their wrong beliefs on the topic.
But then, there's people who've made it an article of faith that Mustachestan is evil. Their reason isn't really the specific or general crimes of Mustachestan, but rather the fact that they've based their personal identity around an ideology which has as one of its key tenets defeating and suppressing the idea of Mustachestan. These people do experience cognitive dissonance at hearing denials of Mustachestan's crimes. They're not interested in evidence-based education because it raises the specter of a discussion-based format, wherein they must, for even a fleeting moment, entertain an uncomfortable idea in order to know what to refute.
I would speculate also that teachers sympathetic to certain other mass-murdering regimes don't want to teach that Mustachestan is evil because of crimes their own favored side is also guilty of, since that would lead attentive students to the realization that what said educator supports is also evil.
My guess is that the latter group outnumbers the former, but either could lead to the same end: a new model of education wherein students must accept as an article of dogma that Mustachestan is evil without ever having been taught why it's evil. What I'm raising is a hypothetical where, 30 or 40 years from now, your average young person will have never heard of a certain major genocide, because their textbooks skipped that part in favor of vague generalities about the nature of evil and conflations of this idea with Mustachestan.
And when, in the spirit of youthful rebellion, many of these decide to buck said dogma and embrace the idea that "Actually, Mustachestan was good" (I.e. your average edgelord Satanist who grew up in a strict Pentecostal household), they won't understand that this is an immoral position to hold. Sure, they'll know that their teachers and society say it's immoral, but they'll have no reason to uncritically accept this, since the entire time it will have been asserted without any proof given.
