Via Twitter, this WSJ essay from a Jewish Rabbi. Emphasis mine.
Despite the strong association of the term with collective Jewish guilt and concomitant slaughter, Sarah Palin has every right to use it. The expression may be used whenever an amorphous mass is collectively accused of being murderers or accessories to murder.
The abominable element of the blood libel is not that it was used to accuse Jews, but that it was used to accuse innocent Jews—their innocence, rather than their Jewishness, being the operative point. Had the Jews been guilty of any of these heinous acts, the charge would not have been a libel.
A point that’s completely and utterly ignored by the left is that Palin has been libeled and viciously so. But when the victim points out a crime has been committed against her, they attack again than rather apologizing. And all this during a debate about the toxicity of political rhetoric!
Murder is humanity’s most severe sin, and it is trivialized when an innocent party is accused of the crime—especially when that party is a collective too numerous to be defended individually. If Jews have learned anything in their long history, it is that a false indictment of murder against any group threatens every group. As Martin Luther King Jr. wrote in his Letter from Birmingham Jail, “Injustice anywhere is a threat to justice everywhere.” Indeed, the belief that the concept of blood libel applies only to Jews is itself a form of reverse discrimination that should be dismissed.
From many of the media reports, I have a sneaking suspician that a lot of the people who are calling Palin ignorant only know about the term because they had a quick read of Wikipedia. In fact, if you believe NewsBusters, they haven’t even read their own archives.