The RealTruthProject (http://therealtruthproject.blogspot.com/2010/09/my-not-really-right-wing-mom-and-her.html) discusses the phenomenon of political outrage chain letters that are based on lies and misconceptions and seem to have been intentionally generated to both misinform and anger.
It isn't exactly surprising to think that there are people intentionally spreading lies and misinformation for political reasons, but it is disturbing. One wonders how this could be countered.
One thought would be to catch each of these deceptive emails, and try to deluge the internet with corrections. "Obama does not grab his crotch at the National Anthem". This might backfire. George Lakoff has argued (for example in "The Political Mind") that countering an argument merely serves as a reminder of that argument. Repeatedly saying "Obama is not an anti-American" might simply strengthen the association between "Obama" and "anti-American".
Another alternative would be to simply flood the internet with equally egregious misrepresentations, only with the contrary slant. For those of us with moral qualms about lying, this is not an attractive alternative.
Perhaps the best approach would be to send mass chain emails that describe events truthfully, but with a tone of outrage.Take for example today's news story about Mike Huckabee claiming that Obama grew up in Kenya with anti-British values (http://www.csmonitor.com/USA/Latest-News-Wires/2011/0302/Mike-Huckabee-caught-claiming-Obama-grew-up-in-Kenya).
An outrage email could have the subject "Very disturbing: Politician spreads lies to undermine our relationship with British allies". This would tempt readers prone to rage at politicians to open the email. However the outrage would be directed at Mike Huckabee for spreading lies about Obama that could potentially damage our relationship with Britain.
And there is nothing disingenuous about this; moral outrage at blatant lying is appropriate.