To quote him:
The term “blood libel” has taken on a broad metaphorical meaning in public discourse. Although its historical origins were in theologically based false accusations against the Jews and the Jewish People,its current usage is far broader. I myself have used it to describe false accusations against the State of Israel by the Goldstone Report. There is nothing improper and certainly nothing anti-Semitic in Sarah Palin using the term to characterize what she reasonably believes are false accusations that her words or images may have caused a mentally disturbed individual to kill and maim. The fact that two of the victims are Jewish is utterly irrelevant to the propriety of using this widely used term.

Just to add in the usages of blood libel by major media over the years, from Jim Geraghty of NRO's growing list...

The Term ‘Blood Libel’: More Common Than You Might Think
January 12, 2011 9:51 A.M.
By Jim Geraghty


The use of the term “blood libel” in non-Jewish contexts is out of bounds, eh?

Andrew Sullivan, October 10, 2008:

A couple of obvious thoughts. Paladino speaks of “perverts who target our children and seek to destroy their lives.” This is the gay equivalent of the medieval (and Islamist) blood-libel against Jews.

Ann Coulter’s column, October 30, 2008:

His expert pontificator on race was The Washington Post’s Eugene Robinson, who said the Pittsburgh hoax was “the blood libel against black men concerning the defilement of the flower of Caucasian womanhood. It’s been with us for hundreds of years and, apparently, is still with us.”

From the Military Religious Freedom Foundation, September 30, 2009:

Almost immediately following the aftermath of the shooting, the Military Religious Freedom Foundation was the unlikely voice that called for the safeguard of Muslims in the armed forces.

Within hours of the news breaking, MRFF founder and president Mikey Weinstein called upon President Barack Obama to “immediately issue a statement as Commander-in-Chief making it clear that there would be a zero-tolerance policy against any member of the U.S. military inflicting harassments, retribution or reprisal against an Islamic member of the U.S. military.” . . .

He criticized former Alaska Governor and vice presidential candidate Sarah Palin for saying that she was “all for” profiling against Muslims.

“We’re not painting all Jews as thieves for Madoff’s economic crimes,” said Weinstein, comparing Palin’s comments to a “blood libel.”

During the recount in 2000:

Florida Democrat Peter Deutsch last night on Crossfire:

Let me just talk a little bit about the whole, I guess, spin from the Republicans about — which has been to me the absolute most — the worst statements I have ever heard probably in my life about anything. I mean, almost a blood libel by the Republicans towards Al Gore, saying that he was trying to stop men and women in uniform that are serving this country from voting. That is the most absurd thing and absolutely has no basis in fact at all.

In the grand scheme of things, the idea that Palin used a phrase associated with one particular, egregious, and historically recurring false accusation to rebut a modern false accusation seems like little reason for outrage. For perspective on what really is worth outrage, the services for 9-year-old victim Christina Taylor Green are tomorrow.

UPDATE: Some more examples, from my side of the aisle:

Jed Babbin, September 8, 2004:

When, in April 1971, John Kerry testified to a Senate committee that “. . . war crimes committed in Southeast Asia [were] not isolated incidents but crimes committed on a day-to-day basis with the full awareness of officers at all levels of command,” he said that the average American soldier who fought in Vietnam was a war criminal. Kerry’s statement was false, a blood libel that hangs in the air to this day.

Michael Barone, November 15, 2004:

And the argument against Michael Dukakis, which he never effectively countered because there is no effective counter, is that giving furlough to people who have life without parole is a position that Dukakis defended over 11 years as governor of Massachusetts or governor candidate, is a crazy law, and he supported it over 11 years. You don’t have to be a racist to want a murderer, whatever his race, to stay in jail and not be allowed outside on the weekend. To say that the American people were racist and they just want black people in, is blood libel on the American people.

John Hood, September 23, 2003: “A ‘Blood Libel’ Against the News & Observer.”

ANOTHER UPDATE: Either Joel Roberts or Andrew Cohen of CBS News (both names are listed), February 9, 2005:

Ward Churchill still doesn’t get it. Even though he has tried to clarify and backtrack upon the worst of his intemperate remarks about the victims of the terror attacks on America, he persists in hanging a blood libel on thousands of victims and, by clear implication, you and me.

Andrew Cohen of CBS News, May 7, 2008:

So-called “judicial activism” occurs, in other words, when it’s your side that lost the case and it is nothing short of a blood libel against judges to accuse them of operating by fiat.

Alex Beam in the Boston Globe, January 14, 2005, discussing the accusation that an official had used the “n-word” in meetings overseas:

My two anonymous sources were making charges that amounted to ‘blood libel’ against former colleagues; that raised the bar for ethical publication.

John Derbyshire, April 28, 2008: “A Blood Libel on Our Civilization.”

AP, July 28, 2008:

Just before Obama spoke, Newsday editor Les Payne had called “blood libel” the argument that African-American journalists could not objectively cover Obama’s candidacy.

ANOTHER UPDATE: Frank Rich, New York Times columnist, October 15, 2006:

The moment Mr. Foley’s e-mails became known, we saw that brand of fearmongering and bigotry at full tilt: Bush administration allies exploited the former Congressman’s predatory history to spread the grotesque canard that homosexuality is a direct path to pedophilia. It’s the kind of blood libel that in another era was spread about Jews.