Not every conservative that says you can choose your sexual orientation is gay, but that argument was started by a closeted gay conservative and was popularized by closeted gay conservatives. And that's the exact same story for most conservative bullshit. They all think they are the Standard Human™ and they feel some shame about part of themselves (because they aren't the Standard Human™) so they force that insecurity on everyone else. The rest of them follow suit as long as a line is already popular enough.