Allegations that Israel plunders and trafficks Palestinians' organs are ugly, false, and harmful to peace efforts. No less dangerous—such libels spread.

The Aug. 17 story by Donald Bostrom in Aftonbladet, Scandanavia's leading daily, has quickly metastasized to mainstream Muslim media, spawning cartoons of Jews stealing body parts and drinking Arab blood. These have been published in Syria, Qatar, Jordan, the United Arab Emirates, and Oman, to name a few.

In...