The Charlie Hebdo massacre was utterly despicable. To nearly everyone, including nearly all Muslims, what the perpetrators did was a terrible moral transgression. From everything I’ve read about the events, there is no doubt that the perpetrators were morally motivated, feeling that they were doing just what virtue required, avenging the satirical publication’s insults to Muhammad. For the killers, the background to the blasphemous cartoons was the humiliation and violence Americans committed against Abu Ghraib prisoners, the invasion of Afghanistan and Iraq, drone killings of Muslims, and so on. Cherif Kouachi spoke in the past about wanting to go to Iraq to fight Americans because he considered what was happening over there to be torture. Alongside these precedents for using violence to right wrongs, no doubt the killers were modeling the suicide bombings and other acts of violent “martyrdom” that are perpetrated nearly every day in Iraq, Afghanistan, Europe, and the U.S.

In the eyes of the perpetrators and their associates, Charlie Hebdo’s cartoonists had committed a terrible blasphemy, so the cartoonists, and anyone who supported or protected or was simply associated with them, deserved to be punished—by death. When the suspects were found, they did not surrender and were killed by the police. If they hadn’t been killed, they would have been tried and imprisoned in punishment for the homicides they committed; in the U.S., China, or Saudi Arabia, they would face the death penalty. In news reports, the Charlie Hebdo perpetrators said they wanted to be martyrs, and some will see their deaths as calls for killing more infidels. Their purported links to al Qaeda could lead France and its allies to bomb al Qaeda or affiliated “targets” to punish them. This could lead to “collateral” deaths that those who direct the strikes may deem a “reasonable cost” for avenging the murders of the cartoonists. Then the families and those who identify with the victims of those bombings will certainly retaliate against French, American, or other targets held collectively responsible. We see much the same cycle of killing in the Islamic State executions of Western captives and Western bombing of people believed to be affiliates or supporters of that group. Before that, there was 9/11, the invasion of Afghanistan to avenge the 9/11 attacks, leading to further retaliatory attacks against Western civilians, and so on.

For a long period of human history, until states emerged, with effective law enforcement and judicial means of dispensing justice and punishment, people often relied on violent vengeance to protect themselves. It was adaptive: the survival and reproduction of the avengers was enhanced by violence that gave them a reputation as people who shouldn’t be messed with. People have often used violence to regulate their relationships. Indeed, as Tage Rai and I show in our new book, Virtuous Violence, when people hurt or kill others—or themselves—it’s usually because they are morally motivated to do so: they feel they should or must use violence to make their relationships right. People use violence to create, sustain, redress, end, and honor their relationships when their cultural models prescribe doing so.

But living in a world of self-help vengeance is terrifying, bloody, and miserable, so when people can count on a chief or state to keep the peace and provide protection, they almost always chose to forgo self-help vengeance. As Steven Pinker shows in his book, The Better Angels of Our Nature, over the millennia and right through the last few decades, violence has been decreasing. All around the world cultural prototypes, precedents, and precepts for violent regulation of relationships once prevailed, but are more or less steadily and quite dramatically being replaced by cultural models for regulating relationships non-violently. But this trend is scant solace for those killed by perpetrators who still believe that they must use violence to make their relationships right.

The moral motives of some people, like the “Unabomber” Ted Kaczynski or Anders Behring Breivik, who committed mass murder in Norway in 2011, are crazy—few or no others recognize their moral ideals. But even these crazy murderers are killing to regulate their relationships, motivated by their solipsistic moral systems. A few generations ago, most parents felt that to bring up their children to be good, God-fearing adults, they had to whip them when they did wrong. Adrian Peterson and some others still think so, but more and more people reject it. Not long ago, in most American states, a husband couldn’t rape his wife; there was no such crime. Most authorities and the general public judged that husbands had near absolute authority over their wives, including the moral and legal right to demand sex whenever they pleased and to use violence to enforce that right. What was thought to be morally natural and legitimate then is now judged to be morally wrong and criminal. Nearly everywhere in the world, people once thought that kings and democratic states should use violence to enforce their authority, including brutal policing, torture, and capital punishment—often excruciatingly drawn out. Everywhere, both church and state once routinely executed anyone who disrespected them.

In America, gangs and fraternities perform brutal initiations. Incas, Aztecs, and Mayans once created, sustained, and redressed relationships with deities by sacrificing people to them, while Plains Indians offered up their own blood or flesh to guardian spirits. Among the Warramunga of Australia, the bereaved injured each other or themselves, while they and the Ilongot of the Philippines killed random outsiders to mourn a death. Most of us today would judge acts like this to be wrong.

Violence is a terrible way to regulate relationships—terrible not just for the victims, but also for the perpetrators, who generally find harming or killing abhorrent, often carrying the trauma with them for a long time afterward. War can be incomparably thrilling and generate extraordinarily deep relationships that are uniquely rewarding and impossible to duplicate in civilian life. Martial arts and football are exciting, for the challenge and the comradeship; violent protests may provide the same thrills. But for the most part, when cultural guidelines point to non-violent ways to create, sustain, redress, terminate, or mourn relationships effectively, people much prefer to avoid violence. The potential for violence is in our genes, evolved as a very powerful potential manner of regulating relationships. But the potential for kindness, devotion, compassion, love, empathy, fairness, justice, respect, patience, reconciliation, and restraint are also in our genes. Whether we are violent or gentle depends mostly on our cultures, and we are collective masters of our cultures.

Our response to the loathsome Charlie Hebdo massacres should be utterly and absolutely non-violent. Violent retaliation only leads to more violent retaliation. But when we make it clear that regulating our relationships to each other don’t require violence, we can stop that cycle. In Baltimore, the Cure Violence program has engaged influential community leaders, parents, and others to tell those who have shot and killed fellow members of the community that killing is intolerable—and when they did so, homicides declined dramatically. In South Africa and many other nations, truth and reconciliation commissions have resolved the moral issues of systematic and particular violence, effectively ending wars and more or less satisfying all parties. We must now stand up not only for free speech, but for freedom from violence, however morally just it feels.