Yes, evil people do exist, my friend. I love your ignorance, don't change.
I will keep fighting for you to keep your ignorance.
Strangely enough, I've looked into that as well. Most people who are willing to go to extremes have been exposed to those sort of traumatic events in their past as well - have been desensitized, or have less quarrals wanting to re-experience traumatic events, even if they induce them themselves. Usually those people are what you'd call 'burned' and dont get very high in bureaucratic ladders.
Then there are psychopths, and sadists (can be 'released' in a societally acceptable way these days) - and again, the bureaucratic process usually is designed to flush them out as well.
(When I was young and in the military, we were used as role playing extras in UN peace keeping mission training, where we would interrupt convoys haggle with the actual soldiers in training, and steal some of their stuff openly - if some of them lost their temper, we would report it, and those cats would be axed from being allowed to go abroad. Just as a small tidbit.)
Then there is a concept called division of power, or four eyes principal, or.. - so you get even less erratic decision making as a result.
Decision processes of dictators (where power is handed over in family succession) are a little different, but their internal logic isn't that of a madman either.
Also - there is a huge sensitivity gap between western societies, and lets say Iran, where people get killed every week at times, in acts of terror, or opposition. So boundaries extend.
But every time - you are told, that you have to get behind an act of lets call it counter terrorism, as the public, you are usually lied to to garner consent.
Now - there is an issue, where sensibilities clash. ('Why terrorism works' (I dont want to explain that)) f.e. and even an issue with sensibilities becoming warped over time (constante state of terror, or wars).
But I can assure you, that everyone wants to sleep at night - so their self images arent those of a villain. Villain is what gets constructed as a societal image.
And in crafting that, you have leeway.
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Decision model of an absolutistic ruler: "I know whats best for my society" (decision processes delegated), smaller evil to kill off the rebels in one swoop. Immanent danger > more casualties allowed. Less precise weapons, more civil victims (there always are, there are no 'chirurgical strikes'). Greenlight it to get a war faster to be over, or to prevent getting toppled. Women and children die. You are coined a villain.
In wars different logic applies, there is also shock and awe used as an actual tool - but usually not as a long term strategic decision by higher ups. Long term oppression (think Ghaza), that might change as well. Logic is always "the lesser evil", or "dehumanizing "the enemy" (not thinking of them as humans anymore)".
In neither case the Disney Villain principle applies. If someone is baiting you with "good versus evil" distinguishing by "dudes" - they are usually engaging in propaganda. Humans have the propensity to become evil in extreme circumstances, and forget about it subsequently (dealing with trauma). Its usually not "a guy" thats the issue anywhere.
The same as it is usually not "a guy" that you should trust in, or that knows what to do, or that has to be protected from criticism.
Once you see, that the enemy is human as well - its not as easy to kill off a dude, by pronouncing that 'he was bad" - which coincidently, they always were in the end. That or marthyrs - isnt that convenient.
And there isnt a society on earth that would pronounce a psychopath to a position of "real" power, if they can help it.
Also read Hannah Arendt on "banality of evil". Its the same thing Freud came to grasp with in his later years. Its the propensity of "normal" humans to become evil situationally thats causing the issue.