Carl is actually better attuned to his world than the older characters who grew up in ours. His cause-and-effect argument was sound, from his perspective and the information he has been given. He is growing up as a hunter-warrior in a nomadic culture, like many humans over the ages, and should not be judged by our standards of civilization. The neighboring tribe wants to kill your people, take your resources, and just raided your settlement. If you come across one of their number and he doesn't surrender immediately and unambiguously, odds are quite high that he will be killed. Even if he becomes a prisoner, he will be a drain your resources. It's not pretty, but what this show is dealing in is brute survival.
He needs some tempering by experience like any youth, but I don't see anything to indicate Carl is a psycho or will be a detriment to the group. His behavior fits the world he lives in.