Exactly. There is a natural aversion to that part of the body and for good reason. Unless, of course, you are a homosexual male.
The sewer system is considered one of the greatest human inventions of all human history because it effectively managed human waste and the really nasty diseases that made people very sick. To intentionally and frequently put a body part in “that area” is not only foolish and unhealthy, it is disgusting for the average person. And if you are Christian, it defies God.
And to claim that it is no different or exactly like heterosexual sex is absurd.
I still don’t get why they don’t try other alternatives. I can understand that someone might be attracted to the opposite gender, but why commit a specific behavior when there are clearly alternatives that are workable, and even less hazardous than the sewer.