Some good answers here already. Purely from consequences it’s necessary to hold people to account. For example even if you didn’t believe in free will at all which is kind of a maximalist argument along the lines of your point (that people are influenced by outside factors, are indoctrinated, are not entirely responsible for their thinking and hate), most agree we still should hold the r*pist to account, we should still hold the murderer to account, we should still hold the arsonist who burned down an apartment with people inside to account. That really only those in the grips of total psychosis, who are suffering from a brain malfunction, who cannot at all tell reality from fantasy are held somewhat harmless for their actions beyond being restrained and treated until no longer a threat to others.

This doesn’t mean it’s not human and somewhat normal to have some pity, to see the humanity in the eyes of even a murdering colonist, the humanity they gave up with their choices to become monsters.

But some people commit acts as adults so far beyond what we can forgive that no apology can suffice, no amount of pleading that they’ve seen the error of their ways can be enough. The extremely rare 1 in a million who decides to atone by working themselves to death in service to their victims can be left well enough alone but most let’s be honest don’t take any actual action beyond crying and booing their own sadness and trauma and playing the victim.

I’m sorry I just don’t think someone who bombs and kills little kids and posts memes laughing about it can do anything to change the weight of their actions and what any decent society must rule is the consequence for such. Those most directly responsible for the violence, for spreading the indoctrination to others, for defending the violence (propagandists) are soaked in blood that can never be washed off. There are those whose situations are more nuanced but there are many whose situation is not at all.

As an aside I look with some amount of skepticism at those who propose that in the west we could at some enormous scale what China did at a very small scale to a small number of high ranking war criminals and a former emperor. Quite frankly the indoctrination runs far deeper here in the west than in China. Liberalism, capitalism have been here for hundreds of years. It’s interwoven with religious dogma, with cultural dogma that is entirely part of the liberal super-structure unlike in China whose culture still had strong communal non-individualist (if feudal/peasant) elements to it. You try and shame a Chinese person from that era with their ancestors and community responsibility and most feel it pretty deeply, you try and shame a westerner and they scoff at you because they, their parents, their parents’ parents were all raised in individualism, in a contempt for the community, in a fuck the world and treat others as stepping stones mentality, in an economic mode that directly rewarded and venerated this behavior.

Frankly in that situation you’re not going to have success, you’re going to have relapses be as common as any success if not more-so. The easier solution, the more merciful for all involved including the millions of jailers you’d need under such a scheme is triaging. It’s the Nuremberg solution for the worst of the worst, for the bottom rungs for whom chance of success is much stronger, re-education.

That kind of thinking is the kind of blind dogmatism that Marxism-Leninism rejects. We say for each nation, for each struggle, learn from the common path but adapt to the unique circumstances rather than trying to copy paste as the Maoists (MLM) do.