I don't know how to explain a fundamental moral principle to you if you don't already know it.
But you really aren't operating on idealism, just some set of rules that has no grounding in how the world operates and therefore no proof. Scientific socialism? What's that?
The less quippy response, and I think this really covers everything you said outside of the Mao case, is that you have the pseudo-religious moral conviction that can only be reaffirmed by tautology and instead of reflecting on its shortcomings, all you're doing is talking in circles.
To give monsters a good life after they've enslaved, raped, tortured, and murdered so many people is to shit on the graves of their dead victims, and spit in the faces of their surviving victims. It is to reward them for their evil -- they've reaped the benefits of the violence they do and are spared the harms. You think war criminals should be allowed to retire in peace and paint in the old age they denied the people they murdered? That's so obviously evil I do not know how to teach you if you don't understand.
Reform is indeed better than causing more destruction for its own sake. I want a better world, with all available resources spent improving the world, not one that is dragged down paying blood taxes for no benefit.
Plenty of people believe in Hell and dance on the graves of war criminals when they die. "Henry Kissinger is burning in Hell" they say. Well what is Hell but divine revenge? It's hypocritical for people to support the idea that a God may be punishing people with eternal torture but clutch pearls at the thought that humans should hedge our bets and make sure war criminals experience a bit of Hell on Earth before they die just in case there is no Hell to receive them when they die. I'm not saying you're a hypocrite by the way, I don't know what your thoughts and claims are, but this is an inconsistent view I have seen people express.
I believe Hell would be unjust and that most secular people who use expressions like that are being hyperbolic, because they recognize the New Atheist truism that even in a retributive framework, infinite suffering cannot be a proportional punishment to any finite crime, no matter how great. I think even a finite Hell would be fucked up and only a very liberal interpretation of Purgatory could be justified. Torture just isn't worthwhile.
I'll also say here though you repeat yourself that what I am doing is not "pearl clutching", i.e. expressing moral indignation. What I am doing is calling it idealistically "grounded" and wasteful. Healthy people don't seek catharsis in inflicting pain on others, so sadism is not an indication that someone should be tortured but that the sadist needs a more medically sound type of help.
Now sure, I can understand foregoing or limiting revenge due to optics and strategy so as to not alienate pearl-clutchers. Fine, to some extent.
If you need to say things like this, subverting what you claim is a moral principle for the sake of "optics", you have a hint that something makes sense. Communists disdain to hide their aims.
And rehabilitating captured enemy soldiers is one thing -- if it can be done, it's fine, and if they were conscripted and are fighting against their will it's even a morally neutral thing with immense strategic value so I support it.
What a fucked up calculus it is when rehabilitating conscripts is merely neutral. I think moralism is not a useful framework, but that's bad even for moralism.
But the higher-ups, the leaders and their army of propagandists, do not deserve mercy. They have caused immense pain in hundreds of thousands to millions of people, and it is only fair that they experience an approximation of a fraction of that pain back.
It doesn't undo the harm they did, there are no ghosts being allowed to rest in peace, it's just a ritual of sadism taken as an axiom.
lmao @ you bringing up Mao when Mao also understood that the retribution liberated peasants took against their liberated landlords didn't need to be endorsed, but didn't need to be stopped either. The oppressors spin the ropes and set up their own gallows.
For all your bluster, you don't actually address Puyi because you know you're fucking wrong. Mao was a champion of rehabilitation in both the Chinese Civil War and the Korean War.
I readily said that violence is sometimes strategically necessary, and the situation with the landlords was very much strategic. Mao didn't have the resources to go around liquidating the landlord class with the PLA, so he had the peasants take it into their own hands. He knew that this strategy would lead to "excesses" carried out against the landlords, but he accepted it as a much lesser evil than the landlords continuing their brutal exploitation of the peasantry. It was rather like that Mark Twain quote:
THERE were two “Reigns of Terror,” if we would but remember it and consider it; the one wrought murder in hot passion, the other in heartless cold blood; the one lasted mere months, the other had lasted a thousand years; the one inflicted death upon ten thousand persons, the other upon a hundred millions; but our shudders are all for the “horrors” of the minor Terror, the momentary Terror, so to speak; whereas, what is the horror of swift death by the axe, compared with lifelong death from hunger, cold, insult, cruelty, and heart-break? What is swift death by lightning compared with death by slow fire at the stake? A city cemetery could contain the coffins filled by that brief Terror which we have all been so diligently taught to shiver at and mourn over; but all France could hardly contain the coffins filled by that older and real Terror—that unspeakably bitter and awful Terror which none of us has been taught to see in its vastness or pity as it deserves.