Reminds me of Dinesh D’Souza, “I was just sharing a hotel room with a young, female staff member. Why would anyone think that’s a problem?”
The other person is the problem, you are just being logical.
Actually you are being a real jerk and rubbing the other person's face in the fact that you care nothing for them.
After the divorce or separation you will cry about how you were always the perfect spouse. And polite people will have to restrain their desire to throw things at your oblivious head.
And they saved money by sleeping in the same bed.