The tricky part is when reputation changes the message. My blanket recommendation is to listen to a doctor's medical advice, but that doesn't cover the possibility of a doctor speaking outside his or her area of expertise. There is something to be said for how a doctor will have broader general knowledge about medicine than the average person, but there are areas of medicine that remain almost entirely unknown even to doctors. When a doctor speaks knowledgably about these unknown topics, then adds the glossy seal of approval - "by the way, this is coming from a doctor" - it forces me to think a little differently regarding my ideas about censorship.
Does this mean that I feel a doctor should only be allowed to speak in the language of proven science? I think what I mean is that when someone in a position of power knows that his or her authority may reinforce speculation, then that person should remind us of the possibility. Prefacing speculation with phrases like "Ignore the fact that I am a doctor for a minute, but I suspect..." may not solve all our problems - there is always someone out there who will believe the remotest of hypotheses - but it should help us see the line between what requires censorship and what should merely be taken with a little extra salt.
