Explain to them that transgenderism isn’t a real thing. He’s been sold a lie by someone that because they don’t like something about themselves they can just identify as something else. That they are likely just gay and they should embrace that and not be homophobic. It’s ok to be gay. That HRT is very dangerous for developing bodies and causes irreversible damage. That no amount of GAC will make him a woman and that suggesting such is insulting to real women and their struggles. Good enough?