Exactly, but as long as he stopped when she asked, he shouldn't be at fault. People can't always help the feelings that they have toward sex so he shouldn't be judged for it. But they have a lot of talking to do. I have to go for the night- I hope you can help her out a little.
I also have a movie recommendation- "Kinsy" with Liam Neeson. Goodnight- I'll catch you later.

Exactly what is this unspeakible act?

Some woman consider that oral or anal... others might define it as something way different involving S&M, skat, golden showers or something else.

But she should never do or allow anything she isn't specifically into or interested in doing.

And has been mentioned. One persons kinky can be another persons boring routine.

Me and my wife for example are pretty open minded. But things like Bondage or S&M are absolute turn-off's to both of us. As are acts involing defication or taking a wizz.

Im sure you've heard the term S&M?
Well Sadists like to inflict pain and masochists like to receive it.
Spanking, bondage, dominance and submission all fall under the category of "kink" which is actually the correct term to use. Kink sexual practices transgress what are considered normal sexual boundaries.
Dypers and defication come under the sexual fetishes catgaory.

Just piling on what's been said...

One lover thought anal was disgusting, another could hit orgasm with it and self stimulation. One person thinks porn is degrating, another finds it a useful "tool" for her bedroom. One lover would never masturbate in front of me while another loved to do it while I nibbled at her ears.

This reminds me of the US supreme court justice who, when pressed for a firm definition of porn, said "i know it when i see it"...