While turning kids into murder implements is a valid criticism of Edgar's moral character it should be kept in mind that the alternative to Edgar burying the memory is the children remembering the fact they participated in several killings, something that would very obviously be deeply traumatic.
Beyond that I'm going to be frank most of your rhetoric is deeply misunderstanding the degree and kind of evil of evil Edgar is: he is, bluntly, not going to go around killing middle managers unless he has an actual reason nor is he going to feed random people to killer plants to test them.
He isn't a random murder maniac, nor is he some generic nebulous cloud of inchoate malice. He has specific neuroses, traumas, coping mechanisms, and ideological stances that all his prior murders can be traced to: the woman at the orphanage he ax murdered triggered Edgar's visceral reaction to seeing children hurt, the security guards died because Edgar reflexively dehumanizes people in uniforms, the people he targetted using the Buddytraps were explicitely those Edgar didn't think would ever face real consequences, and when he threatened to blow up ACME regional headquarters it was because it was the only way he could realistically stop them dumping with the resources he had available at that time.
Edgar is, in other words, a character with actual psychology that dictates his actions, not a cartoon whose going to feed assembly-line workers to the woodchipper because they work for Raytheon. He isn't going to be evil for the sake of being evil: every action he takes will ultimately have at least some internal reasoning or explanation.
Beyond that, as mentioned, you're overestimating how evil Edgar actually is: yes, he is a man who brainwashes children and uses them as murder implements. Unlike Clancy, however, who would do that out of political convenience and to spread paranoia about the threat of peoples children in order to further destabilize society and kill at targets she couldn't otherwise get to, Edgar is at least trying first and foremost to help the children and is at least attempting a form of harm reduction. Between Edgar, Clancy, and the FUSA, Edgar is, frankly, the least likely of the trio to turn those kids into outright child soldiers.
He's evil, sure, but he's very much the lesser evil.
This is frankly another issue: firstly, what Edgar is doing isn't actually the same and any rhetoric that compares him to the government or vault tec is immensely underestimating how bad the other two parties are. Sure, brainwashing is obviously, like, very morally fraught, but FUSA brainwashing exists on every level of media and education across the entire nation from birth to coffin. There is quite literally no way to avoid it, especially since the government is obviously suppressing any information that could lead to these children developing political views the gov't doesn't want.
Beyond that, "brainwashing someone to not be fascist" isn't actually morally equivocal to brainwashing someone into a fascist, especially since the underlying motives and goals are completely different. It's not good, but fascism is, like, an innately evil belief structure that is literally built on cruelty and malice.
And that's before we get into the fact that Vault Tec and FUSA are both, y'know. Genocidal.
Like to be blunt here: you kinda have a very naive understanding of the political situation and it's moral dimensions. Edgar could go all in on mind-control and at the end of the day he would still be the lesser evil compared to the other parties being discussed. I cannot stress this enough: FUSA is morally equivocal to nazi germany. And like, this isn't just a you thing here, but I'm kind of getting the vibe a lot of people don't actually realize what that means or how dire the situation is. Death camps, human experimentation, genocide. Again, genocide. Genocide. Every day, at a minimum, tens thousands of people in FUSA are being murdered by the government deliberately with companies like Vault Tec and RobCo assisting. Adults, women, and yes, children are constantly and ongoingly being systematically killed by FUSA, who is also per canon exporting this abroad by annexing and occupying foreign nations, so like it's not even purely internal cruelty.
And even if we discount the genocide fact we also have the fact that Vault Tec and the government are both partially responsible for ending the world. And, y'know, the vaults: another reason the comparison with Vault Tec fails is that even if mind control bad Vault Tec has done significantly worse than researching and using mind control technology.
