Anyone who makes an alarmist prediction may not be questioned. If the Mayan Calendar says the world is coming to an end on December 20, 2012 – and then it actually happens. Who would want to be culpable for questioning it?
Likewise, when the eminent Dr. Paul Ehrlich said that we would all be dead by 1980, what if turned out that he was correct? Same for the CIA’s dire warnings of global cooling in 1974.
If an alarmist says something bad is going to happen, you should be required by law to listen to them.