A policeman walks past Iranian nuclear scientist Mostafa Ahmadi-Roshan's car, which was bombed by a drive-by motorcyclist in Tehran Wednesday, killing Ahmadi-Roshan.

REUTERS/IIPA/Sajad Safari

n Iranian scientist from the Natanz uranium enrichment facility was killed Wednesday by a bomber on a motorcycle who attached a "magnetized explosive device" to the scientist's car. Tehran blamed the assassination — the fourth such attack in two years — on Israel and the U.S., which is tightening sanctions to force Iran to halt its nuclear program. The Obama administration condemned the killing of the scientist — Mostafa Ahmadi Roshan, 32 — and said the U.S. had nothing to do with it. But GOP presidential hopeful Newt Gingrich has said we should be "taking out their scientists." Should such killings, in a sense, be welcomed if they help prevent a belligerent Iran from building nuclear weapons, and potentially destroying many more human lives?

Killing civilians is never acceptable. This is terrorism, pure and simple: The victim of this assassination was a civilian, says Andrew Sullivan at The Atlantic. And there's a word for the killing of a civilian on another country's soil: Terrorism. If, as many believe, this was the work of Israel's intelligence service, it's almost certain that we got word ahead of time. So if you're applauding this murder, ask yourself what the U.S. would do "if another country started placing car bombs on U.S. soil to kill American scientists."
"The terrorism we support"

By starting this war, Iran provoked the killings: The effort to stop Iran's nuclear program is a war, and, for the U.S. and Israel, "it's not a war of choice," says Amir Oren in Israel's Haaretz. If those countries were to sit back and allow Iran to build its first atomic bomb "tensions in the Middle East would intensify to an intolerable level." Whoever killed Mostafa Ahmadi Roshan was sending Iran's leaders the message that, until they relent, nobody in their nuclear program is safe. Now, at least, they will "do some soul-searching."
"Assassins of nuclear scientists are sending a double message to Iran"

These assassinations might make matters worse: Soul-searching? Don't count on it. Whoever is behind these assassinations — Israel, the U.S., Iranian dissidents — might be making a grave mistake, Trita Parsi, president of the National Iranian-American Council, tells CNN. Iranian leaders haven't waved the white flag or scaled back their nuclear ambitions since the wave of assassinations began. "Arguably, the incentive for the Iranians to go forward... has grown, because now they're under such critical threat."
"Who's killing Iranian scientists?"