There is an ethical way to do anything. Comedy is no exception. Sadly, comedy is a case of extremes, to do anything other than an extreme would be hypocritical.
It is simply this: either everything is sacred, or nothing is sacred. Those are the only ethical ways to do comedy. It simply that you must treat all subjects equally, be the person, place, idea, etc. Thus, either everything is open to being the subject of a joke, or nothing is.
A great many people want to tell that there exist subjects that should never be joked about. What these subjects are vary from person to person. Usually the subject that want treated as sacred is based in some great personal pain, but why should anyone's pain be treated as special?
We all have pain, none of it special. So to me, nothing is sacred.