The horrible murders of rabbis during their morning prayers in Jerusalem, killed in their prayer shawls in a synagogue. I was thinking about this horrific act, and ISIS beheading a journalist in northern Syria, while walking this evening along Broadway on Manhattan’s Upper West Side.

Then I found myself face to face with a protest in front of Symphony Space, where Idan Raichel, a singer from Israel, was scheduled to play with Vieux Farka Toure, a musician from Mali, in west Africa. They were “building bridges.”‘

At the same time a mob outside was trying to stop the show, screaming about Israel’s crimes against the Palestinians, rapping a song about how “Gaza is us.” The disconnect between the morning’s murder and this protest was surreal. I understand that a permit probably was issued before the murder occurred, but then I realized that no murder of innocent Jews would ever stop these fanatics.

They do not protest against Saudi Arabia, or Kuwait, about their mistreatment of women and gays or their support of terrorism. They do not protest against Assad’s killing more than 100,000 of his countrymen. For them, all the problems in the world begin and end with Zionism.

What, I wondered, did they invest in their cause? What do they get out of it, other than the social thrill of hanging out with other extremists? And I realized that it is safe and interesting for them to hang out in this inexpensive moral blanket, which covered all wrongs with one wide swing. They will go home feeling good about themselves, even if it inspires more terrorist acts and beheadings.

After all, it’s our demand for meaning that creates this endless supply of causes and priceless ideology.

EDITOR’S NOTE: Idan Raichel and Vieux Farka Toure, well-known, well-respected musicians who both explore world music from a dizzying range of traditions, have aroused the ire of Boycott Divestment Sanction groups because Mr. Raichel is Israeli. The November 18 concert was the target of a protest by one such group.