Simply grant the religious people God's existence and the logic kinda makes sense. I understood it as something like this: Eternal suffering is the greatest suffering someone can endure. Since this suffering is so great, you owe a duty to everyone to save them from this suffering. When you sin you are more likely (/will depending on who you talk to) to suffer for eternity. You thus owe a duty to someone to keep them from sinning. Sex with someone of the same gender is a sin. Thus, you owe a duty to everyone to keep them from having sex with someone of the same gender.

Not that I agree with all that, but it makes sense why believers of this are so resistant to the idea of same sex marriage. And other then that I agree, I dont get how this one sin is made out to be the sin that will ruin one's chance of getting into Heaven. Hopefully I'm right, because when I discussed this with my extremely christian friend, he told me I was going to hell. Thanks, friend haha. But I agree with you, shit doesnt make sense to me since