Looking for info to disprove this stigma, I don't really have much other than one academic research paper I found but I don't think if the guy I'm arguing with would be willing to sit through and read that. He dismissed it as queer theory which he says has been "debunked" idk what the hell queer theory is. Anyway from what I can tell with this dude the simple and more obvious the better but it must also be backed by peer reviewed research
Then tell him to stop shoveling his internalized homophobia out. Ask him where he learned about it and see what empty, hollow response you get.
He is most likely hiding other reactionary beliefs since the one he picked right now is pretty crypto-fascist.