I think he was "snookered," but only because he wanted to be, like with a seduction.
With all due respect and with no malisciousness, I think you are being snookered by Dan Rather.
Rather had this information for months , no way a man with his experience could not have known it was phony. IMO
Rather is complicit in a plot to destroy the President, he is no longer reporting news he is involved in Partisan politics. Which is fine for as long as you admit it, but when you report news as a neautral . and get paid by a news organisation to slant the news it isnt ethical.