Isn't it too much after you kill the second or third kid?

For the last 80 years they've been told that the people they're killing aren't human beings. At a point they check out and are okay with it.

It's not that they see the people they're fighting as human

I'm saying that's not a shield against it. Genocidaires dehumanize their victims and they still get fucked up by their own actions and what they're taking part in. It's not about morals or consciences or anything like that, it's just people not handling that sort of violence and horror well at a fundamental level. That's not to say "oh it makes them sad, it makes them unhappy, it makes them regretful" because it can just as easily make them worse and more violent and unstable, it's just to say it's something that actively attacks and corrodes their own humanity. They can psych themselves up and dehumanize their victims and beat their chest as loud as they want, as loud as they need to to push themselves to actually do it, but they're still going to be broken by it in some way.

This isn't something original to Israel, obviously, though that provides a very clear and visible example of a population trying to keep themselves whipped into a bloodthirsty frenzy and breaking at the seams because of it. I know it happened to the Nazis too, and that there's research on that and how Nazi ideology tried to recuperate that self-destruction through violence by lionizing it and making it a pillar of their ideology. I'd assume it's just a universal phenomenon, that such violence just kind of does that to people regardless of how they try to psych themselves up and cope with it.