Quote the cwckiIt's less about Chris have "the mind of" an 8 year old and more like saying "an African Grey has the mind of a 5 year old human." As in, that doesn't mean you should treat an African Grey like a 5 year old human, it just means it has comparable functionality.
As it's been said and demonstrated, Chris is capable of learning that he shouldn't do something, but he doesn't understand why. Children get punished and feel embittered about it, and later learn that their punishment was just and that they were acting out of order. This never registers to Chris, he's perpetually in a mental state of adolescences. Always getting burned, not understanding why, only that the big mean world doesn't want him to do it for some reason. You can't go here, you can't touch this. He knows he can't do these things, but he absolutely thinks he should. He has the sense of entitlement of an infant.
the behavior of small children, who, isolated from the real world by a lack of comprehension and limited mobility, believe themselves to be godlike beings. This belief is gradually destroyed as the child goes to school and encounters outside authority, leading to their acknowledgment of the fact that they are, in fact, ordinary people. Of course, since Chris is not only autistic but also extremely sheltered, he still manages to cling to this belief by focusing on specific aspects of his life and constructing elaborate fantasy worlds.