A very important article has been written analyzing the reasons for the media's silence, "The Bush Rule of Journalism", By Robert Parry, January 17, 2005, Published on "consortiumnews.com":
“Don’t take on the Bushes” is becoming an unwritten rule in American journalism. Reporters can make mistakes in covering other politicians and suffer little or no consequence, but a false step when doing a critical piece on the Bushes is a career killer.
"The latest to learn this hard lesson are four producers at CBS, who demonstrated inadequate care in checking out memos purportedly written by George W. Bush’s commanding officer in the Texas Air National Guard in the early 1970s. For this sloppiness, CBS fired the four, including Mary Mapes who helped break last year’s Abu Ghraib torture scandal.
"A painful irony for the CBS producers was that the central points of the memos – that Bush had blown off a required flight physical and was getting favored treatment in the National Guard – were already known, and indeed, were confirmed by the commander’s secretary in a follow-up interview with CBS. But even honest mistakes are firing offenses when the Bushes are involved."