Creature of Mad Enthusiasms

I dunno. Being fooled about something that important leaves a bad taste in people's mouths, just like all those "I'm dying of cancer, please give what you can" emails that we know are 95% likely to be hoaxes. It lowers people's willingness to put themselves out for a good cause, because they hate being played for a fool, even if they know the source was dubious. And it also lowers their ability to respond effectively, as in the case of people who try to call in favors the time someone cries wolf. Using that as part of his defense is just trying to pass on the blame, from the person who behaved like a moron to the people who "should have known he was just a moron".