Wayne LaPierre, of the National Rifle Association, at the Conservative Political Action Conference in March. PHOTOGRAPH BY SAUL LOEB / GETTY

In the language of today’s National Rifle Association, “an armed society is a polite society.” The aphorism, borrowed from the science-fiction author Robert Heinlein, is the inspiration for one of the N.R.A.’s most popular T-shirts, which bears the word “COEXIST,” spelled out in brightly colored ammo cartridges and guns. To promote the shirt ($17.99), the N.R.A. store says that Heinlein’s quote “emphasizes the independent, tolerant nature of gun owners in a fun and thought-provoking way.”

It is a vision at the heart of the modern gun movement: the more that society makes the threat of violence available to us, the safer we will be. In forty-eight hours this week, the poisonous flaw in that fantasy has been exposed from multiple angles: on Tuesday, two police officers in Baton Rouge, Louisiana, fatally shot a black man, Alton Sterling, while trying to arrest him. Some reports say that, before police arrived, he was openly carrying a gun, which, under the makeshift patchwork of American gun law, would have afforded him more legal protection, not less. Louisiana is one of the forty-five states that allow residents to carry firearms openly in public, and though Sterling was a convicted felon (and therefore probably ineligible to obtain a concealed-carry permit) police could not have known his criminal record before investigating him. It was absurd not to ask whether a white man, exercising his right to open carry, would have been approached differently.

The next day, during a traffic stop in Falcon Heights, Minnesota, a police officer fatally shot a black man, Philando Castile, who, according to his girlfriend, Diamond Reynolds, was licensed to carry a concealed firearm. According to Reynolds, who was in the car and broadcast the aftermath on Facebook, Castile had told the officer that he was carrying his gun, but when Castile reached for his license and registration, he was shot. In the hours that followed, as America turned, once again, to the ritual of mourning the killings of black men by police officers, the N.R.A. was silent. Its official Twitter feed, which often draws attention to cases of police questioning gun owners for exercising the right to carry, said nothing, even as the silence became conspicuous. (@CoolJ90: "@NRA care to come to the defense of a man murdered by police who had a license to carry his weapon?")

For critics of the N.R.A., it was an awkward exposure of what is usually left unsaid: the organization is far less active in asserting the Second Amendment rights of black Americans than of white ones.

On Thursday, the politics of race, guns, and security exploded in a horrific attack on law enforcement. While protesters in Dallas marched in the name of Black Lives Matter, denouncing the latest killings, a sniper ambushed police, killing five and wounding seven others, along with two civilians. In a standoff, a suspect was killed by a police bomb. Dallas police later identified him as twenty-five-year-old Micah Xavier Johnson. In his statements to police, they said, he “wanted to kill white people, especially white police officers.” Three other suspects reportedly were in custody.

In turning guns on police, the Dallas ambush scrambles the usual polarities of gun politics. For more than two decades, the N.R.A. has maintained a facsimile of respect for law enforcement, reflexively announcing its devotion to “warriors” and “heroes”—even as it has pushed to relax laws that police routinely describe as a threat to the safety of their officers and the public. Last year, under lobbying pressure from the N.R.A., the Bureau of Alcohol, Tobacco, and Firearms abandoned an effort to stop the sale of armor-piercing “cop killer” ammunition that authorities have tried to ban for thirty years.

After each high-profile public massacre in recent years, the N.R.A. and its allies have deployed a reliable strategy: deflect criticism from the basic problem—the unqualified availability of military-grade weapons—by fixating on technical details that serve their political ends. After the massacre in San Bernardino, they emphasized that, despite strong gun laws in California, the killers had legally purchased some of their guns—as if that proved that gun regulation is useless, and so society shouldn’t bother. After the slaughter in Orlando, in an effort to defuse attempts to impose stricter regulations on AR-15s, the military-style rifle used in San Bernardino and many other attacks, gun-rights advocates fixated on the fact that the Orlando killer did not use an AR-15. (He used a similar military-style rifle, produced by Sig Sauer.) It was, in retrospect, an especially shortsighted strategy: by drawing attention to the broader range of weapons that are widely available to civilians and capable of inflicting mass harm, gun-rights advocates inadvertently aided their opponents by making it newly evident that banning AR-15s alone would not solve the problem.

The Dallas ambush will be harder to explain away. There is much still to learn about the guns involved, but early videos appeared to show a man executing a police officer using a military-style rifle, which has proved to be especially deadly for American police. The Violence Policy Center, a gun-safety group, noted that, in 2014, the most recent year for which information is available, “one in five law enforcement officers slain in the line of duty were killed with an assault weapon." The center’s executive director, Josh Sugarmann, said in a statement, “Responsibility for this lethal assault falls directly at the feet of the gun industry, which designs, markets, and sells the military-bred weapons necessary for such attacks. They must finally be held accountable.”

The Dallas ambush has also exposed an uncomfortable fact for the gun-rights movement: for decades, even as it maintains its abstract tributes to law enforcement, it has embraced a strain of insurrectionist rhetoric, overtly anti-government activism that endorses the notion that civilians should have guns for use against American police and military. In a 1995 fund-raising letter, the executive vice-president of the N.R.A., Wayne LaPierre, called federal law-enforcement agents “jack-booted thugs,” and suggested that “in Clinton's administration, if you have a badge, you have the government's go-ahead to harass, intimidate, even murder law-abiding citizens.” In Texas, where the police ambush occurred, an open-carry advocate last year urged the killing of state legislators if they do not approve a more relaxed policy. (“They better start giving us our rights or this peaceful non-cooperation stuff is gonna be gamed up . . . We should be demanding [Texas legislators] give us our rights back, or it’s punishable by death. Treason.”) At the annual N.R.A. convention last year, the board member Ted Nugent said, “Our government has turned on us.” Stopping short of calling for violence, he urged members to focus their ire on “the bad and the ugly.” He said, “It’s a target-rich environment. If it was duck season, there’d be so many ducks, you could just close your eyes and shoot ’em.”

The consistent failure of our politics to take reasonable steps to prevent guns from getting into the wrong hands makes it difficult to predict with any confidence that even the slaughter of police officers will alter the frozen politics. But it may have a subtler effect, causing gun owners to reconsider whether the N.R.A. truly has the country’s best interests at heart. More than a hundred million Americans live in households with guns, but many remain largely uninvolved in gun politics. The N.R.A. has between three and five million members, which means it represents only a sliver of American gun owners. Moreover, even among its members, many are unconvinced, I and others have found, by the belligerent rhetoric; they own and love guns for a variety of reasons—from sports to hunting to self-defense—and they overwhelmingly support reasonable steps to prevent innocent people, civilians or police, from being killed by gunfire.

On Friday, after hours of silence, the N.R.A. issued a statement from LaPierre, who had authored the “jack-booted thugs” letter. This time, he expressed “the deep anguish all of us feel for the heroic Dallas law enforcement officers who were killed and wounded, as well as to those who so bravely ran toward danger to defend the city and the people of Dallas.”

The N.R.A.’s explicit call for a more armed society reveals the lie behind its homage to “coexistence.” By directing rage against the government, by preventing politicians from heeding the overwhelming demands of their constituents for broader background checks, by endorsing Donald Trump’s plan for mass deportations and bans on Muslim immigration, the N.R.A. has assembled a volatile case against the idea of coexistence—and then disavows the result when it explodes.