I am ashamed to say, that in the past, this has been me. Not quite the same, I didn't threaten to cheat, but I let my frustration at a poor sex life get the better of me and when I look back, I am ashamed of how I acted. She deserved better from me.
While not there now, I went through a long spell (8 years) of being rejected for sex about 90% of the time. I felt unattractive, unwanted and unappreciated. I do a lot around the house, do more than half of the school runs and childcare etc.. and cook, do food shopping too.
I have a high sex drive, and while we used to be compatible, that waned for various reasons.
I think my mistake was that I didn't really try to understand her point of view, to understand why she was rejecting me and took me longer than it should to apprecaite that my approach was far from ideal.
On reflection, it seems obvious now, but at the time I was so upset and frustrated that I didn't act in a way that I would now.
We came through it, I have apologised and worked through a lot of my and her issues and are in a much healthier place.
I am not for a second justifying what he has done, I think it is deplorable, but I simply wanted to say that I have been like it myself in the past and I feel shame for it.
Perhaps having a conversation and open discussion about things may help as it did with me. Make him understand, because sometimes we just don't think enough about the other point of view, only see things from our side, and it results in bad behaviour.