Credulity and the end of the world

Natural credulity is often an innocent enough thing. And in most cases, it can be harmless. But what about when the natural credulity in certain people coerces them to act or think in a way that is directly harmful to them? How do we prove to these people that they are believing in dangerous ideas?
To more fully explore this issue, I'm going to set up a hypothetical situation, but one that has mirrored events in real life.
Let's imagine that a regular, blue collar man, about 40, comes into the public eye with the claim that the angel Gabriel visited him and commanded him to take dictation. This man has a book, which is the direct message from God and that he has been told that the world will end on October 27th, of this year. He rapidly manages to get his face on the TV and radio and the public get a lot of exposure to him. He further claims that people who do not believe in his message, will not be part of the elect on the final day and will be left behind to suffer in the mighty tribulations to follow.
Now, this isn't a very far fetched hypothesis. Men and women have made claims like these before. A mammal called Harold Camping predicted that the Rapture and devastating earthquakes would occur on May 21, 2011 with God taking approximately 3% of the world's population into Heaven, and that the end of the world would occur five months later on October 21. 

Wrong on all three counts and yet he still has followers! 

And here's the thing about my hypothesis: people would believe it. I remember the Camping affair and I noted how many otherwise rational and reasonable people nervously checked their calendars and watches leading up to this prophesied end of the world. Of course his followers believed wholeheartedly, despite no evidence to back up the ludicrous claim at all. Especially noticeable is the fact that Camping's previous prophecies had both been wrong.
So, how do we deal with this mentality? How do we challenge lunatic claims of this kind? As we now know, Camping and the hundreds of other such claimants throughout human civilization have all been wrong. Yet, I'm sure that in the next few years, another such mammal will make another such claim and despite the fact that no one has ever been right, people will believe it.
Natural credulity is born out of several different realities in humans. First, we are naturally fearful of the cataclysmic. The smoking towers in Manhattan at 9/11 was about the most apocalyptic thing I had ever seen, until Katrina and the tidal wave of 2004. Having been raised in a fundamental evangelical household, I was taught that the end times would be foretold by wars and rumors of war and of earthquakes and mighty weather. Imagine what people who were listening to Jerry Falwell and Pat Robertson were thinking when they, too, witnessed these terrible events. 
So it is that we fear our own immolation and I think people generally hope that if they believe end times claims, that is will somehow save them from the fear and pain of a terrible death.
But I also think that natural credulity has its basis in a desire to belong. When a larger group believes something, even something as ludicrous as a end of the world prediction, people jump on the bandwagon in order to feel as though they are part of something larger than themselves.
Human behavior is a difficult thing to understand, in that—in almost every case—it seems to work in antipathy to the common good. Think about trampling people to escape a fire or the inability to move out of the way of a onrushing car.
So it is that
we need skepticism to help us when claims like the ones above are made. When the sky rolls back like a scroll and the face of the deity himself announces the end of the world to the entire planet, I might be a little more willing to believe it. However, until that time, we need to arm ourselves against the tendency toward natural credulity. The world isn't going to end and when it does it will likely be by the hands of some radical fanatic than by the predictions of a TV minister or cult leader.
Skepticism as a shield against these and other outlandish claims is the best way to proceed.