For instance, if I were to come up to you with fomenting zeal, proclaiming that the earth was flat, rather than round, you would certainly think that my conjecture is mad because all evidence points to the contrary. And it is this same zeal that magnifies my insecurity, for my argument is not based on evidence.
Now, if you were absolute in your beliefs, would you block me? Would you ignore me or shun me? I'm sure you could find a photograph of the earth - so why would you be insecure about your position?
Such is the case with matters of faith. The faithful stifle any sort of dissent because they are insecure and unable to undo counterpoints with something as simple as a photograph.