ON May 12, The Times published an Op-Ed article by Edward N. Luttwak, a military historian, who argued that any hopes that a President Barack Obama might improve relations with the Muslim world were unrealistic because Muslims would be “horrified” once they learned that Obama had abandoned the Islam of his father and embraced Christianity as a young adult.

Under “Muslim law as it is universally understood,” Luttwak wrote, Obama was born a Muslim, and his “conversion” to Christianity was an act of apostasy, a capital offense and “the worst of all crimes that a Muslim can commit.” While no Muslim country would be likely to prosecute him, Luttwak said, a state visit to such a nation would present serious security challenges “because the very act of protecting him would be sinful for Islamic security guards.”

At a time when fears about Obama’s security keep bubbling to the surface and an online whispering campaign suggests that he is secretly a Muslim — call him by his full name, Barack Hussein Obama, some Times readers demand — the Luttwak thesis was a double whammy: Obama cannot escape his Muslim history, and a lot of Muslims might want to kill him for trying.

Many Times readers saw the article as irresponsible (“gasoline on the fire,” said Paul Trachtman of Tierra Amarilla, N.M.) or false (“Islam is not like our hair or the color of our skin, which we inherited from our parents,” said Ali Kamel of Rio de Janeiro). The blogosphere lit up with assertions that Luttwak did not know what he was talking about.

The Times Op-Ed page, quite properly, is home to a lot of provocative opinions. But all are supposed to be grounded on the bedrock of fact. Op-Ed writers are entitled to emphasize facts that support their arguments and minimize others that don’t. But they are not entitled to get the facts wrong or to so mangle them that they present a false picture....