Why does "it" have a dehumanizing connotation?

There are a number of questions here on gender neutral pronouns, and one of the things that always comes up is that "it" should never be used to refer to a person (usually an adult). The general reasoning for this rule is that "it" is used to refer to animals (in some cases), and inanimate objects. Basically, it's considered dehumanizing.

What I haven't seen, though, is an explanation for why it's considered dehumanizing (other than the circular logic that it's only used for non-human subjects).

Solution 1:

Old English was highly inflected and the third person singular personal pronoun had masculine, feminine and neuter forms. The neuter form was, in the nominative, hit, which became modern English it. English grammatical gender has disappeared, but we retain he and she to refer to nouns which clearly describe male and female entities, mostly people. The neuter it refers to everything else.

Solution 2:

The fact that it is not used for humans is why its use on humans is dehumanizing. We don't refer to those odd-shaped things at the ends of your arms as "paws"; if I call them "paws" I am connoting "animal" instead of "human". The long history of it reinforces it. Also, we have pronouns for humans. So using a non-human pronoun for a human must imply something, right? Otherwise, why not just use the human pronoun?

The original choice of words may be arbitrary. The fact that the original speakers distinguished between humans and non-humans may be a relic of culture or random chance. But the centuries of usage reinforce the meanings. It is a feedback-loop. Children learn not to use the language a certain (arbitrary) way and that learning becomes entrenched. The connotations become a feature of the language because of continuous reinforcement. Then, when someone violates the convention, it draws attention to itself.