Sex has a wide variety of meanings. If you find yourself in trouble you can affect your entire family. Even if he didn’t do it. (although Monica says that he certainly did) He had the eyes of the people on him and should have acted properly, so that there was not a hint of immorality. If you’re a married man, you can’t go flirting with other people other than your wife. The guy could have saved himself a lot of trouble.
Stick to one woman, it’s much safer that way. You never know who’s watching. In Bill’s case it was the entire free world.