It isn't dehumanizing to consider someone "a source of information or expertise". It's humanizing in that those are predominantly human things. And that's one of the primary senses of the word. It seems uncharitable to assume someone must mean some other sense.

The meaning of a word is much more than its definition in a dictionary. Context matters. Humans are animals, yet saying that someone is an animal might mean anything from praise (You're killing it, you animal!) to contempt (Stop behaving like an animal!).

Suppose I call you an ape. It's literally true, isn't it? Yet you would naturally assume I meant it in a dehumanizing way.