How can people believe things that are clearly false?
The Dan Rather story led us to this article by Robert D. Sider on Tertullian. Although renowned for the phrase, apparently Tertullian didn't really say "credo quia absurdam" (I believe because it is absurd), rather "certum quia impossibile" (I am certain because it is impossible).
Either phrase is about the power of religious faith to overcome logic, as in the case of miracles.
That is what the CBS forgeries represent in the faithful mind of Dan Rather--the documents are miracles from on high to destroy the "Evil Bush." They have provided the 'smoking gun' of Bush's guilt in shirking National Guard duty. Like a relic of the Holy Grail, to doubt them is to challenge an entire faith. Thus, to preserve their own faith they must ignore the facts of this case. This religious impulse to believe the absurd is what lies at the heart of Rather-gate. Rather is a true believer. And in a form of religious fanaticism he places his faith in things which are clearly impossible. The greater the absurdity, the greater the faith. Thus, Dan Rather is demonstrating his fideism by sticking to his absurd story.
However, unlike Rather, Tertullian actually accepted the authority of reason--Logos:
"In the second and third centuries Christians of both East and West generally accepted a common mythos about God and the world. They believed that the world was rationally ordered, because it was created by God through his reason, his Logos. The same Logos spoke to man through rational terms in the Revelation embodied in the Bible and in Jesus. Even apart from Christ, men have caught glimpses of the truth, whether borrowed from the Bible or gathered from the order of nature. Unfortunately, the demonic, in one form or another, has entered to distort the vision of man, so that pagan philosophy never attained the wholeness and integrity of truth. Such integrity can be found only in Christ, the Logos; but because he is the Logos the integrity of truth implies the necessity of rational perception. Differences in apologetic aims, in individual style, and in personal temperament led to formulations of the relationships between faith and reason, and Christianity and philosophy which undoubtedly varied in tone and emphasis, but the common commitment on the part of all the major Christian thinkers of the second and third centuries, including Tertullian, to a belief in Christ, the Logos, eliminated fideism as a possible mode of Christian self-understanding."
Dan Rather's actions in this case reveal that he doesn't recognize the authority of Logos, only Mythos.