Here’s my question.

[Acrobat]

I don’t think most theists care what you do personally with your genitals, they do care whether you try to push your particular sexual morality on to them or their children.

I don't think this is true at all.  Theism has - and always has had - a long history of trying to regulate the sexual mores of other people.  Rules against polygamy, polyandry, clan marriage, incest, homosexuality, masturbation, etc. always arise either directly from theism or as a sop by secular authorities in an attempt to appease theists.

Boru

No societies have pretty much always placed restrictions on sexual practices of one form or the other, incense, sex with minors, animals, etc... China has a variety of limitations on sexual activity, and it’s not theistic. Societies draw lines around such behaviors, some more liberal and some more restrictive. If the porn industry and brothels wanted to participate in HS senior job fair, I would think most atheists here would take issue with it.

Christianity, as far as the NT is concerned has next to nothing to say about legalities, or legal restrictions of anything, let alone sex, only with the morality of it all.