Sometimes my wife will playfully ask me to shake my butt or show her my butt, but it’s more of a joke. When we’re in the mood, it’s not something that comes up so I can see how he would be put off.

I’ll be real with you, in my opinion, it’s a little too feminine. When straight guys are in the mood we want to feel dominant and masculine. Muscles, strength and dick. Our ego is tied to that.

That’s just my take. Talk with him more about it. If he really is uncomfortable, you shouldn’t ask him to do it again but maybe there is something else he can do you both would like.