Yes, the three figures you cite have all made a difference on the world stage. But if I had the opportunity to speak to one of them, and he told me that he was, in part, motivated by his religious beliefs then I would probably hear him out, nod politely and change the subject as soon as possible. I just don't believe that religious faith is a prerequisite for doing great things.

But, more fundamentally, the faithful believe that they are in possession of 'absolute truth' and that this truth is contained in ancient texts of dubious or obscure provenance. I see nothing wrong in subjecting such beliefs to scrutiny - especially if the holders of the beliefs demand respect or special privileges.