Urban America has for the last week been burning. In several cases, protests that began over a valid cause—the wrongful death of George Floyd by Minneapolis police officers—have been prominently accompanied by riots.

In New York City, stores have been looted across multiple boroughs. In D.C., major civic institutions like the Lincoln Memorial and World War II memorial were defaced. In Portland, rioters set fire to a police station and courthouse, and in Philly did the same to police cruisers.

In these and other cities, officers have been shot, run over, hit by bricks, and had explosives thrown at them. Store owners have been beaten by mobs, as have innocent bystanders for simple gestures like carrying an American flag. And crime syndicates have organized mass looting of stores and ATMs.

In cities with a coherent grip on reality, what to do should be obvious: use law enforcement to stop it. But leaders in a number of U.S. cities seem disinclined, at this point, to do so. Instead, some mayors and governors, fueled by a mix of politics and ideology, can barely condemn the riots, much less call larger police bodies to stop them for fear of being seen as opposing the entire protest.

The lead example is New York City mayor Bill de Blasio. The radical nature of his politics—past, and present—has been well-documented. Now we’re seeing a real-time experiment of how this radicalism plays out during a crisis.

Even as overt chaos ensued this past week—the looting of Macy’s, the ransacking of SoHo, the hurling of a Molotov cocktail into a police car, and much more—De Blasio has downplayed the riots. On separate occasions, he has falsely claimed that the violence results from a few anarchists; called for the unjust firing of an officer who was trying to keep order; and defended his daughter, who was arrested for being in a large crowd throwing objects at the police. When asked why, on behalf of containing coronavirus, he would ban religious services but allow violent riots, he cited “400 years of American racism.”

But de Blasio’s most blatant error has been refusing to bring in the national guard, something urged by Governor Cuomo and President Trump. Other mayors and governors have also refused or made minimal use of it. Portland has struggled with violent Antifa protests on and off for years, and this time is no different, with footage of fires being set and open beatings in the street. But Ted Wheeler justified his refusal to deploy the guard by saying that he “stood in solidarity for our demonstrators fighting for justice.”

President Trump could respond by citing the Insurrection Act to send the military into these cities.

The law is seldom used and not ideal since, in this case, it would represent the overriding of local decisions by the federal government. But 58% of voters support the measure, according to a poll by Morning Consult, likely because they don’t see an alternative. Americans dislike that their cities and institutions are getting destroyed, and don’t see in local leaders anyone who will stop it.

The riots were occasioned by the protests, and the protests were triggered by the tragic George Floyd incident. The idea among those defending the violence is that it’s the only way to spearhead reforms in the American police system.

That premise is questionable. A 2018 study by Gabor Nyeki of Duke University found that “peaceful protests made legislators vote more liberally, consistent with the goals of the Civil Rights Movement. By contrast, violent protests backfired and made legislators vote more conservatively.”

A Stanford University study published in response to the 2017 Charlottesville protest found that racial justice advocates got less support for themselves—and more for their opposition—when otherwise-sympathetic observers learned they acted violently.

It’s plausible that following George Floyd’s death, massive peaceful protests would have led to officer convictions and police reforms anyway. Many of those reforms, such as weakening unions and ending qualified immunity, have floated around in recent years. The violent protests, by contrast, have harmed people who aren’t to blame for George Floyd’s death; and the violence is enabled by politicians who won’t stop or even condemn it.