By Larry Keane, National Shooting Sports Foundation

Things haven’t been going too well lately for New York City Mayor Michael Bloomberg. The billionaire mayor and his anti-gun group, Mayors Against Illegal Guns (MAIG) ran into criticism last week from Senator Chuck Schumer for attacking Democrat senators who voted against gun-control legislation.

“Frankly, I don’t think Bloomberg’s ads are effective,” Schumer told Time magazine. “The Mayor of New York City putting ads against people in red states is not going to be effective.”

But Schumer’s comments were nothing compared to what came next.

At a New Hampshire stop on the Mayors Against Illegal Guns “No More Names” bus tour, organizers read the names of people killed by “gun violence” during the six months since the tragedy in Newtown. But there was something amiss: included among the names read was Tamerlan Tsarnaev, one of the Boston Marathon bombers. Observers were outraged.

While the reporter that covered the event for the New Hampshire Union Leader didn’t mention this egregious misrepresentation until near the end of his story, others paid much more attention to it. The news of this slap in the face to the victims of the Boston bombing spread quickly over the internet, picked up by the Washington Examiner, National Review, Fox News and the Drudge Report. A Bloomberg spokesperson eventually apologized for the mistake.

But the story didn’t end there. Tsarnaev was not the only gun “victim” on the bus tour’s list. It turns out that one of every 12 names on the Bloomberg “victim” list are crime suspects – including the likes of California cop killer Christopher Dorner. Bloomberg and MAIG’s worldview is so skewed, they think murderers are actually victims!

With this flub, Bloomberg has actually done our work for us, illustrating that firearms are often used to neutralize criminals or terrorists bent on mayhem. After all, that’s why the police carry them. But they are equally useful in the hands of law-abiding citizens when first responders aren’t present to stop a criminal in his tracks.

Now Bloomberg’s people say they are going to “scrub” the list but the damage to his credibility can’t be reversed. And that has consequences in politics. In New Hampshire, there is mounting pressure on the mayor of Dover, the only MAIG member in the state, to resign from the group. Other politicians all across the country are having to reevaluate whether they can believe any of the claims made by MAIG, since this episode makes it clear that the group doesn’t even bother to check its facts before parading them before the media. And the bus tour faces an uncertain future, now having put itself in the box of having to decide which “victims of gun violence” are good or bad.

The bell cannot be un-rung. And this bell tolls for the credibility of any claims made by Bloomberg and MAIG. Mayors and other politicians across the country have now been warned.

Larry Keane is senior vice president and general counsel for the National Shooting Sports Foundation. Follow him on Twitter at @lkeane.