A few more changes first.

"While I've removed the nudity taboo, why not remove a few more?" thought John.

"O.k., so lets see... sex is now a perfectly acceptable form of recreation, and it is perfectly normal to ask for it, and it's considered impolite to turn it down unless otherwise engaged. Female bisexuality is now the norm while men are either totally straight or totally gay. Of course this is possible because there are no longer any STDs in the world and women now only ovulate when they want to, which means no periods and no unwanted pregnancy... And since I'm reworking the female body, women will now always orgasm when their partner does, no matter how much or little stimulation their actual genitals have received. It will just be a natural response."

Hmm what else?

"Oh, because turning down a request for sex without a good excuse is considered rude, it is never challenged. People are simply unable to engage in sex with unwilling partners for any purpose."

...That should do it, thought John.

"Let's find someone to test this out with," he said to himself.