I believe that doomsayers are in a no-lose situation -- If they're right, they boast they were right. If they're wrong, then they say it was better to be prepared and safe than sorry.

I see a parallel with leftists and racism. When there is actual racism, they boast they were right. When there is not, they themselves do racist things and cause people to start thinking it really is a problem; some of whom become so jaded that they slowly start becoming actual racists.