"It" has a pretty clear meaning in English, and it is not as a pronoun for people.

You seem eager to reduce this to "just" a pronoun issue, but it's not the same as calling someone "he" or "she", whatever they might prefer.

No one gets to single-handedly (re)define the English language for everyone else. "It" in this usage does not fall in to normal English usage, other than to mock people. That they want to use it nonetheless or whatever reason, that's fine with me. I will always listen to that and do my best to oblige with that within reason. However, radically different meanings for words in common grammatical structures, for me, falls outside of "within reason". Other people may choose different, and that is fine too.