I definitely don't endorse doing it deliberately, because obviously using the wrong pronoun when you do know their preferences is always bad. But I do think there's a difference between using it like that and using it when you genuinely don't know, since it is one of the most common, if not the most common way to refer to a person of unknown gender. The word itself doesn't do the damage in the case you're describing, but rather the intent is what makes it malicious.