[Those words make Casey hesitate a little, debating what to say. He can't criticize every adult that asks difficult things of children. Sensei had plenty of expectations of him, because the world they lived in only had so much room for gentleness and softer opportunities. Once he reached an age where he could contribute, he was expected to, same as everyone else in the resistance. They'd protected him throughout his childhood, and one day it was time to give back, so those younger than him could grow up safely, too. He hadn't even been a teenager when he started training for patrols. And... he'd wanted it, the chance to step up and prove his worth, show them their efforts in raising and training him was worth it. To unburden them with some of the loads they'd been carrying his whole life and before. He could never curse them for asking him to take part in helping to protect their little corner of shelter in a dying world.

This conversation is for Peter's sake, though, and he can't say that Rue is wrong, either. In a different world, it would have been wrong for them to ask him to take part. But in a different world, they wouldn't have had to ask at all. Finally, he opts for,]

It's better if everyone works together, doing whatever they can... pushing their limits but not beyond. We managed that much at the end of the world, so why can't a world with so much more and so many people do it too? Why wasn't there someone to help him, or even do it for him so he could be a kid?