Appearing on Fox News Sunday this week, National Rifle Association executive vice president Wayne LaPierre was pressed about the controversial ad the group created in the wake of the Newtown, Connecticut school massacre that referenced the armed protection President Obama's daughters receive. Even as host Chris Wallace belittled as “ridiculous” the ad's premise that all children deserve the same kind of protection that the president's children have, LaPierre defend the ad and said, “Tell that to the people of Newtown.”

“So they should have Secret Service”? Wallace asked.

In response, LaPierre propagated a favorite falsehood of the pro-gun media lobby [emphasis added]:

LAPIERRE: No, but what they should have is police officers or certified armed security in those schools to keep people safe. If something happens, the police time-- despite all their good intentions, is 15 to 20 minutes. It's too long. It's not going to help those kids.

In the wake of the Newtown shooting, LaPierre bemoaned the fact kids aren't safe at school, in part because it takes police 15 to 20 minutes to respond to a deadly shooting like the one in Connecticut.

But that's not true and it's time the news media start calling out anti-gun control extremists like LaPierre and Larry Pratt, , the executive director of Gun Owners of America,  among others, who keep peddling the obvious falsehood in the press.

Fact: The Newtown police station is located approximately two miles from the Sandy Hook Elementary School. There's no way it would have taken law enforcement 20 minutes to respond to the first 911 calls reporting gunfire at the school. (Local cops could have run from the station and been at the school in less than 20 minutes.)

Fast-acting Newtown officers “made it in under three minutes, arriving in the parking lot while gunfire could still be heard,” according to New York Times interviews with the first responders that day.

But if you listen to LaPierre as well as other anti-gun control advocates who are making the media rounds, you're led to believe gunman Adam Lanza roamed the hallways of Sandy Hook for nearly half an hour killing people at will before law enforcement finally arrived; that terrified teachers and students were “waiting 20 minutes for the cops to show up,” as one pro-gun blogger claimed.

It's not true. The claim is pure gun lobby propaganda.

The frightening specter of defenselessness is projected to boost the NRA's claim that the only way to combat gun violence in school is not to control the sale and distribution of guns, but to put armed policemen in 98,000 schools in America. Other gun advocates use the phony 20-minute premise to bolster calls for allowing concealed weapons in schools.

Since the December 14 massacre, the 20-minute myth has been widely repeated among right-wing media outlets.

• “It took the police 20 minutes to arrive at Sandy Hook. By the time they got there, it was over. [National Review Online]

• “When seconds count, the police are only minutes a third of an hour away.” [Blogger Glenn Reynolds]

• “In the short run, stopping the next Sandy Hook means ending the deadly policy which gave the killer 20 minutes (until people with guns, the police, finally arrived) to fire 150 shots and repeatedly change magazines, murdering at leisure.” [Volokh.com]

Unfortunately, the 20-minute myth got an early boost from CNN.com, which posted an inaccurate timeline of the school massacre. CNN's faulty claim that first responders arrived at Sandy Hook “about twenty minutes after the first” 911 calls was quickly embraced by right-wing bloggers who mocked the police's slow response time.

But that single, erroneous report certainly can't justify the continued misuse of the 20-minute myth, since the vast majority of Newtown reports got the facts right.  Contrary to CNN timeline, it was widely reported last December that police and first responders arrived at the Newtown crime scene "instantaneously," "within minutes" of the first 911 call, and "minutes after the assassin began his rampage."

And two days after the shooting rampage, audio from Newtown police scanners was made public. It confirmed that officers were reporting back from the school just a few minutes after the first school calls came into the dispatcher that day.

Still, the 20-minute myth serves a political purpose, so people like factually challenged gun extremist Larry Pratt have used the concocted claim repeatedly in the media:

• “The solution is for people to be able to defend themselves at the point of the crime and not wait for 20 minutes for the police come after everybody is dead.” [Dec. 18, CNN]

• "And Newtown was the same, a school where nobody was able to have a gun, even if they had a concealed carry permit, which you can get in Connecticut. Nobody was able to shoot back. They had to wait some 20 minutes for the police to get there. That's unacceptable." [Dec. 28, Fox]

• “Especially if you're telling the potential victim you can't be armed. You have to wait for the Cavalry to get here five, 10 or in the case of Newtown 20 minutes later. I find that unconscionable.” [Jan. 12, CNN]

*Well, the armed teacher is going to have a lot more chance stopping a mass murderer than the police who take 20 minutes to get there, as they did in Newtown, and that's not an extraordinarily long response time. [Jan. 17, Australia Broadcasting Corporation]

Pratt's sinister assertion is pure fabrication. If gun advocates continue to peddle the lie, it's up to journalists to call them on it. The falsehood purposefully hinders attempts to debate the pressing issue of gun violence, and serves an insult to the Newtown police officers on duty that dark day in December.