Purely devils advocate, but maybe its not that different from peeing in the shower? I mean its gross but at least they are doing it at the moment they are washing themselves so end result is still a clean person (assuming they are properly washing their ass andtoesafterwards).  That being said, I cannot fathom doing it while another person is in the shower with you. You want to wash your own shit off of your foot, thats your business. Why the fuck would you subject someone else to having to wash YOUR shit off of themselves?