Does Anders truly "win" by being simply in confinement forever, rather than being dead? What does he gain? His life? What life? Playing PS1 games forever, seeing the same four walls forever, acceptable but certainly not impressive meals forever. There is not a single thing anyone can do to him or anyone else to undo what he did, and causing him suffering certainly doesn't bring back any children. More importantly, killing him does not make any of the damage he caused go away.

Americans love to piss and moan about all the freedoms we supposedly have, but are conspicuously unsatisfied with merely removing said freedoms as punishment for crimes.

Maybe they don't think "freedom" is that important or meaningful

There is continued harm though. Every day he is treated well, every day he gets food and shelter and care is food and shelter and care paid for by you, that could have been spent on others.