The three most visible forms of Christianity to Americans (and probably world wide) are The Catholic Church and the sex abuse scandal, Evangelical fundamentalists ( Think Pat Robertson or James Dobson and the entire city of Colorado Springs), and more frequently far-right neo-fascist movements.
You can't blame people looking elsewhere when that is the face of a faith. It's a shame Gary North is a popular theologian, and scary how much influence he has, while no one really knows about this man ( and associated people)
https://www.truthdig.com/articles/americas-street-priest/
Maybe that's the way it should be for true believers, they do the right thing solely to do it without thought to reputation or reward.
It's silly to think there will ever be enough LGBT folks to impact population growth. There are a lot of reasons people are having less kids, economics chief among them, don't worry about everyone "turning gay" and causing some population or extinction event lol, man climate change will surely kill us all before a mass gay wave LOL
People wanting equitable treatment, their rights that all humans have, supposedly from God, is not an agenda.