There has been little discussion about the real reason Joe Wilson was sent to investigate the yellow cake story. He wasn't sent to investigate, per se. He was sent as cover for his wife, who was the real WMD expert in the family, so she could tap her connections and find out what was really going on. From the little I've read, Wilson's report is a masterpiece of providing plausible reasons why the suspicions were unfounded, but it was clearly a cover for his wife's conclusions based on her covert investigations.