Christians literally go door to door: “Knock Knock Knock. Have you found Christianity? I’ve chosen a christian way of life and I think it’s a great way of life. I think you should choose to be christian. I think you should raise your children to be christian. I think we should teach christianity in school. I think we should elect christian leaders. I think we should have a christian society.”
So they think gay people go around going: “Knock Knock Knock. Have you found gayness? I’ve chosen a gay way of life and it’s a great way of life. I think you should choose to be gay. I think you should raise your children to be gay. I think we should teach gayness in school. I think we should elect gay leaders. I think we should have a gay society.”
Which is of course as ridiculous as thinking: “Knock Knock Knock. Have you found left-handedness? I’ve chosen a left-handed way of life and it’s a great way of life. I think you should choose to be left-handed. I think you should raise your children to be left-handed. I think we should teach left-handedness in school. I think we should elect left-handed leaders. I think we should have a left-handed society.”
(Now it’s not just gay, it’s trans too.)
I think it’s more that “these people” didn’t used to ‘exist’ in their world: Sexual minorities weren’t talked about and were invisible for the most part. But since Stonewall and AIDS, LGBT+ people first decided and then learned not to hide themselves. Suddenly someone who you thought of as normal has ‘become’ gay. You obviously knew them well, it’s not possible they were hiding something from you, and there’s no chance your observations were incorrect - clearly, instead of you being wrong, something happened to them, something ‘turned them gay’ - it must have been the frogs, or music, or DnD, or something, it’s just impossible you were wrong!