(1) For the past two and a half years, MoveOn.org welcomed racist, anti-Semitic, and anti-Catholic hate speech along with 9/11 conspiracy theories at its Action Forum.
(2) MoveOn's exercise of editorial control ("exercise of editorial control" is the key phrase) over the Action Forum makes it 100 percent responsible for the content. MoveOn's moderators were very diligent about finding and deleting posts that were critical of MoveOn.org while letting the hate speech stand.
(3) The rest of the MoveOn community voted overwhelming approval, usually ranging from 70 to 95 percent, of the hate speech.
(4) MoveOn itself (NOT the Action Forum) published a bulletin that cites anti-Semitic sources in Counterpunch magazine, and also an anti-Catholic cartoon that showed Pope Benedict waving a gavel in front of the Supreme Court.
(5) The candidates named above have refused to disown and repudiate MoveOn.org's endorsement and/or monetary support. Compare to Ronald Reagan, who refused to accept the Ku Klux Klan's endorsement. (Don't hesitate to compare MoveOn.org to Nazis and the Ku Klux Klan, noting that the hate speech in question was quite suitable for Klansman and/or genuine Nazis.)
(6) The hate speech in question included a blood libel of Jews that says the Talmud commands Jews to hate and slaughter non-Jews, Jews are more loyal to Israel than the U.S., Jews control all the media, African-American soldiers should be segregated and disarmed as potential mutineers, Condoleeza Rice and Colin Powell are "house slaves," "The Catholics are raping your children," and "Catholic Pedophiles of America." (More here: http://www.stentorian.com/MoveOn/sideshow1.html)
Note that the anti-Catholic hate speech will, if published in Northeast Pennsylvania, Philadelphia, and probably the Pittsburgh area, be very harmful to the Casey campaign because Casey has openly refused to repudiate MoveOn.org despite requests from Jewish and Catholic organizations.
My experience is that MoveOn.org and its defenders-- two seem to have taken their Web sites down today for some reason-- are totally defenseless against this.