I’m not sure Shack is on the down low, but he is a sexual deviant at a minimum. I think like most he is sickened by the stuff gays do to each other. I just don’t see him as someone who wants fecal material on their cock.
That said, I wouldn’t be shocked if he is into shitting on women. He seemed to be the type to humiliate women to make up for their overall rejection of him.