The only reason they persist is because the exceedingly gullible left-wing portion of our population is so very eager to believe it. Anything, and I mean anything at all that casts Dubya in a bad light is latched on to by these folks without question. They are completely unable to reason their way past their biases to see the utter improbability of much of the nonsense they swallow. Example:
http://forums.pelicanparts.com/showthread.php?threadid=249455