It's about keeping control. Christian churches simultaneously 1) Make sex an unmentionable, forbidden thing for everybody who isn't married and; 2) promise that heterosexual sex in marriage is going to be the most amazing thing for everybody.

So, they get church members hyperfixated on sex, at the same time that they're denied satisfaction. The goal is to get young people to marry other Christian church members. Then, once they're married, they're hooked. They quickly have lots of unprotected sex, and make a baby. As the church members mature, they may have doubts, but to reject the church becomes tantamount to rejecting their spouse and children. Outside of the church world, they have no idea how to make social connections.

Also, exercising harsh control over the satisfaction of church members' basic biological appetites supports church members' general lack of independence and reinforces the absolute authority of church leaders to control people's lives in other matters besides sex.

Rank and file church members care about other people's sex lives so much because they have been denied freedom in their own sexual lives. Christian church leaders care about other people's sex lives so much because they know that if church members catch on that it's healthy for adults to have consensual, pleasurable sex on their own terms, the authority of the church will disappear.

Cats and cat ladies are unacceptable to Christian Nationalism, because they refuse to be leashed.

To learn more about nutty Christian Nationalist obsessions, read Donald Trump’s Army of God.