CBS correspondent Lara Logan apologized on “60 Minutes” last Sunday for that program’s deeply flawed account of how four Americans were killed at a diplomatic compound in Benghazi. It turned out that their primary source, a government contractor named Dylan Davies, was never at the compound and lied repeatedly about his role in the whole tragic episode.

The program “had been misled” by Davies and “we are very sorry” about putting him on the air, Logan said. “The most important thing to every person at ‘60 Minutes’ is the truth. And the truth is, we made a mistake.”

The truth is “60 Minutes” made many mistakes, not just one. The truth is they badly mangled their apology. The truth is they owe us all a more candid and comprehensive explanation of exactly how and why they screwed up so badly.

This is not about politics. This is about journalistic integrity.

“60 Minutes,” now in its 46th season, proudly calls itself “the most successful television broadcast in history.” That reputation is based on fearless, unflinching reporting. None of its journalists would ever let a subject get away with the kind of half-hearted, mealymouthed explanation Logan offered. And that includes Logan herself.

Yes, the right-wing seems obsessed by Benghazi. Yes, they have propounded all sorts of crazy conspiracy theories. And yes, the CBS story triggered a new round of recrimination against the Obama administration.

But that’s not the point. The point is that major news organizations should live by the same standards of transparency and accountability they demand of others.

Legacy or mainstream outlets like CBS are under ferocious assault from rising rivals and declining revenues. They continue to play a critical role as providers of impartial, independent information. But they will only survive by living up to the highest possible ethical standards. And so far, CBS has failed that test.

Jeff Fager, the chairman of CBS News and the executive producer of “60 Minutes,” told the Huffington Post that “60 Minutes” had spent “more than a year” reporting the Benghazi story and spoke to “close to 100 sources in the process.” Yet somehow they never figured out that their main source was a liar.

The evidence was clearly out there. A report written by Davies’ employer, Blue Mountain, contradicted the “60 Minutes” account. Davies, who was ordered to stay away from the compound the night of the attack, said he lied to his employer to cover his own insubordination.

For some reason, Logan and “60 Minutes” chose to ignore that huge warning sign and believe his tattered tale. As press critic Jay Rosen put it: “When your key source tells two different stories, something is seriously amiss.”

It gets worse. An FBI report sided with Blue Mountain and also undermined Davies’ story. Yet CBS — in “more than a year” of reporting — never unearthed that damning document.

Then there’s the smelly book deal. CBS owns the publisher Simon & Schuster. One of their imprints, Threshold Editions, which specializes in conservative books, was publishing a memoir written by Davies. In her on-air apology, Logan never even mentioned that conflict of interest or considered whether the CBS investment in Davies’ book contributed to the network’s collective blindness.

Even after others started questioning the “60 Minutes” report, CBS adamantly defended its work. In an email to the Huffington Post the day before the whole affair blew up in his face, Fager wrote, “We are proud of the reporting that went into the story.”

That level of arrogance and self-delusion recalls what happened in 2004, when another CBS star, Dan Rather, aired and then defended a bogus report accusing President Bush of using political pull to evade the draft during Vietnam and join the National Guard. An independent panel blamed the network’s catastrophic mistake on “myopic zeal,” and that phrase could apply to Logan’s report as well.

Steve teaches a course in media ethics at George Washington University and constantly warns his students about one of the most serious ethical traps a journalist can fall into: wanting a story to be true. That wanting can have many motives — bias, ego, fame, greed — but the result is the same. It can cause even good reporters like Rather and Logan to shut their eyes, miss the signs, ignore the warnings.

“Credibility is really the most important thing we have,” says Fager, and he’s right about that. But now the credibility of CBS and “60 Minutes” is badly stained. And they have to come clean. Quickly and completely.

(Steve and Cokie Roberts can be contacted by email at stevecokie@gmail.com)