The Oxford English Dictionary traces singular they back to 1375, where it appears in the medieval romance William and the Werewolf.
That’s irrelevant. Men still can’t become women no matter what pronoun they decide to call themselves. What does the Oxford English Dictionary say about biology?
That's irrelevant also? I said nothing except that they can be singular.
Look up the word “implication” next. Jesus Christ.
Look up straw man,