But memes don’t just happen through curious symbiosis. As Evgeny Morozov, the author of “The Net Delusion,” told me, “It’s not necessarily true that memes are born rather than made.” In this case, a ferociously anti-Islamic Copt named Morris Sadek labored hard to interest an Egyptian journalist in the movie; only then did the infernal cascade begin.

New media often need the help of mainstream media before viral critical mass is achieved. Once it is, the algorithms kick in. Outfits like YouTube are agnostic intermediaries. They want, as Morozov put it, “more clicks, more traffic, more knowledge about viewers and so more advertising.”

And here we are after a week of engineered tumult. The right thinks its case is proved: “You see, we told you so, the Arab Spring was a false dawn. Muslims are incapable of democracy. They are all anti-Western fanatics. Obama was wrong to support the democratic transformation that has brought Islamic parties to power.”

The White House is on the defensive; it even requested at one point that Google, the parent of YouTube, consider removing the movie — an ill-considered request wisely resisted. Free speech is meaningless if it does not extend even to views that are loathsome.

In fact the violence does not change the critical evolution underway in the Arab world, one that needed more support from Obama, not less. Mohamed Morsi, the Egyptian president, was slow to react to violence. But it is far better to have his Muslim Brotherhood grappling with Islamic extremists than an isolated U.S.-backed dictator; and the debate now raging from Cairo to Tunis — a debate that would have been impossible before the Arab Spring — is a necessary part of the slow evolution of societies from terrorist-breeding passivity to citizen-breeding agency.

This change is generational. The folly of this September may be viewed one day as part of the evolution of the Brotherhood toward the conservative pragmatism that has served Recep Tayyip Erdogan’s Justice and Development well in Turkey.

That, I know, is an optimistic scenario. Memes have their own destructive energy. Listen to Benjamin Netanyahu on CNN eliding the truth for maximum panic: “All the things that you see now in these mobs storming the American embassies is what you will see with a regime that would have atomic bombs. You can’t have such people have atomic bombs.”

Who are “such people”? No matter that these were Arabs, not Iranians. No matter that they were far from Tehran. No matter that Persians despise Arabs and vice-versa. Netanyahu understands marketing: keep it simple in a hyperconnected age because you won’t be wrong for long — and the dead can’t issue a correction.