I agree with MSNBC. I find it hard to believe that Gov. Chris Christie knew nothing about his staff’s plotting a massive traffic jam on the ramp to the George Washington Bridge for political retribution.

On the other hand, I also find it hard to believe that Obama didn’t know his own IRS was auditing his political enemies.

And I find it hard to believe that Obama didn’t know you wouldn’t be able to keep your doctor under Obamacare.

But most of all, I find it hard to believe that MSNBC host Al Sharpton didn’t know Tawana Brawley was lying when she claimed to have been gang-raped by rogue cops on the Wappingers Falls, N.Y., police force.

Back in November 1987, 15-year-old Tawana Brawley was found curled up inside a plastic bag in an apartment building parking lot. She had feces and racist graffiti all over her body, her clothing was torn and burned, and she was apparently unconscious.

When she emerged from her (fake) unconsciousness, she claimed she had been held captive in the woods for several days, while being raped and beaten by six white men, including policemen and the local prosecutor.

The story being utterly preposterous, every law enforcement agency in the universe was called in to investigate — the FBI, local, county and state police. Gov. Mario Cuomo directed the state attorney general, Robert Abrams, to investigate Brawley’s claims.

MSNBC’s Al Sharpton was one of Brawley’s “advisers” throughout this massively expensive investigation, along with lawyers Alton Maddox and C. Vernon Mason — both later disbarred.

Eight months and 1.3 million taxpayer dollars later (in today’s dollars), the purported attack was exposed as a complete fraud. It turned out that Brawley made up the gang-rape story to avoid explaining to her volatile stepfather why she hadn’t come home for four nights straight.

Among other findings, the grand jury’s 170-page report noted these facts:

— Witnesses saw Brawley getting into the plastic bag by herself, and then hopping around in it before curling up into a ball on the ground.

— The hospital rape tests were negative and no semen was found anyplace on her body.

— She had no recent bruises or other marks on her body consistent with rape.

— Hospital technicians who evaluated Brawley concluded that she was faking unconsciousness.

— Brawley was well-nourished, had clean breath, no bruises or injuries to her body and was not suffering from exposure, despite temperatures having dropped to freezing several times when she was allegedly being gang-raped in the woods.

— Witnesses had seen Brawley in a vacant apartment where she had once lived during the period of the alleged attack.

— In that apartment, investigators found charred fibers matching the burnt clothes Brawley had been found in, the source of the material that had been stuffed in her nose and ears, and the feces that had been smeared on her. Investigators even identified the dog whose feces it was. Her dirty clothes were still in a washing machine in the building.

At no point did Sharpton question Brawley’s story or urge her to recant. To the contrary, as the case fell apart, Sharpton’s demagoguery rose to Olympian heights.

He branded Abrams “Hitler,” called Gov. Mario Cuomo a racist, and demanded that Cuomo appoint Maddox special prosecutor on the case. (It was a reasonable request: Maddox had accused Abrams of masturbating to photos of Brawley.)

Even in 1997 — a decade after Brawley’s story had been proved a hoax beyond a scintilla of a doubt — Sharpton arranged for her to give a speech to his United African Movement at a Brooklyn church.

I find it hard to believe that Al Sharpton did not know Brawley was lying about being raped by a Nazi cult on the Wappingers Falls police force.

Brawley’s boyfriend later told Newsday that she had admitted to him at the time that she cooked up the story with her mother. Is it believable that she didn’t also tell her trusted adviser Al Sharpton?

While a story about white supremacist cops raping and torturing a teenage girl may not have the flashy news value of traffic patterns in northern New Jersey, trust me, the Tawana Brawley case was a big deal at the time. Lots of people were irreparably harmed because of Sharpton’s outrageous conduct.

There was the falsely accused prosecutor, Steve Pagones, whose life was ruined by Sharpton’s monstrous accusations.

There was Bill Cosby and Mike Tyson, who embarrassed themselves by briefly believing Sharpton. (Imagine how rare and difficult it is for Mike Tyson to experience embarrassment!)

There was the Wappingers Falls police officer, Harry Crist Jr., who committed suicide a few days after Brawley was found in the plastic bag — and was immediately accused of being one of Brawley’s rapists by Al Sharpton. (It was later determined that he had committed suicide after failing the test to become a state trooper for the last time.)

How do you think his parents felt having their dead son accused of gang-rape in the wake of his tragic suicide?

But why limit the list of Sharpton’s victims to the facts? Let’s take a page from MSNBC, and posit a series of “What if?” speculations.

What if there were women who were raped, families whose homes were burglarized and children who got lost on their way to school and froze to death because the entire law enforcement apparatus of New York State was busy working the non-existent rape case?

Leave aside MSNBC’s wishing-and-hoping method of reporting a scandal. (What if we find out Chris Christie has ordered murders?) Does MSNBC really think Al Sharpton is the guy who should be accusing Christie — as he did this week — of putting politics above “people”?

I’d recommend the universal condemnation of his fellow man, but couldn’t MSNBC at least take the maestro of the Tawana Brawley hoax off the “How Can He Not Have Known?” beat? As a matter of basic decency, Al Sharpton should never be allowed to accuse anyone of wrongdoing, especially about who knew what when.

What about the rest of the MSNBC news team? Could Chris Matthews add to his repertoire of do-you-believe questions (in evolution, in global warming, that Obama was born in Hawaii) one question to Sharpton about whether he really believed Tawana Brawley? Are we supposed to believe that Sharpton’s colleagues don’t know about his appalling behavior in the Tawana Brawley case?

What kind of culture exists at MSNBC to encourage such willful blindness?