Ah, but the Terminator DOES act like a child. He acts upon pure id and simple instruction. His mental immaturity is, in fact, a part of why he loses in Terminator 1, and is core to the character development in Terminator 2. He is "innocent". There's plenty of scenes in T2 where the actual literal child is giving him morality, sociality, and life lessons, because his own mind is less developed than that of said child. While I would not pretend to know the machinations of how a pedophile works internally, I leave that to your experienced mind, The Terminator does act like some real children would if you'd give them a machine gun, I imagine, knowing the callousness and carelessness of youth.

And that's yet again a reason why it is difficult to define in fictional settings with exceptional circumstances.

But here's a key point. Because the Terminator LOOKS old, you're fine with it, despite the EXACT OPPOSITE being the purpose of Law (It is to protect the innocent regardless of appearance, not protect people who look innocent regardless of actual). You're starting from a biological purpose standpoint, not a legal or societal one: You do not risk harm people before sexual maturity because it puts at risk the future reproduction of your species, but turn a blind eye to those who are past sexual maturity physically, a literal blind eye, you did not see the clear evidence across four hours of film footage that the whole point of The Terminator is that it is not socially mature. A fine standpoint, truly little is more concretely moral than our base evolutionary psychology, but that does not map well to fiction. Exceptions in real life, for example the profoundly disabled, also exist to this measure you're using, but that likely will not impact your day-to-day life.