In just about every vibrant progressive social movement, there comes a moment when a psychologically or emotionally disturbed person, an agent provocateur, or a political extremist commits an atrocious act that is seized upon by the state and/or the Right to try to discredit or outright repress the movement. Regardless of the motivation behind the action, it is sufficiently heinous that confusion develops within the movement.

It is here that the movement can lose both its momentum and a segment of its less committed or more ambivalent supporters.

With the recent killing of two New York City police officers, the movement against police violence is in a pivotal moment. Intense and manipulative efforts are underway to paint those who have protested police brutality, or even those who have simply spoken up against it, as having blood on their hands — that figures like Rev. Al Sharpton and New York City Mayor Bill de Blasio, and not unremitting police brutality, have created the tension between police and the community.

But this anomalous (if egregious) violence against police officers cannot be used to stop a nonviolent movement.

The Haymarket Massacre is still the paradigmatic case of the state using a violent act to justify repression. In 1886, at the height of the movement for an eight-hour workday, a bomb was set off at a worker rally in Chicago’s Haymarket Square. The rally was called to both protest police killings of worker protesters and to support striking workers fighting for the eight-hour day. When police attacked the demonstration, a bomb was thrown. To this day no one knows who set off the explosive, including whether it was an agent provocateur or an activist.

What is known, however, is that the government used the bombing as a pretext to discredit the protests and the workers movement, suggesting that the entire movement was comprised of supposedly violent anarchists. Charges were brought against key leaders of the movement and in a kangaroo trial, eight individuals were convicted for their alleged involvement in the bombing. Four were subsequently hanged.

The reaction by police unions, the Right and much of the mainstream media today is eerily reminiscent of the aftermath of the Haymarket massacre. In this moment it is critical that progressives forcefully counter these arguments. They are cynical and disingenuous efforts to discredit and derail one of the most important movements of the recent past. Let us be clear about what has transpired.

First, an apparently mentally and/or emotionally disturbed man allegedly attempted to murder his girlfriend in the Baltimore area, before allegedly killing the two officers in New York City. This individual had no connection with any social justice movement, had no apparent connections with New York, and was certainly not a leader of the movement against police violence.

Second, the tension that exists between the police and communities of color was not manufactured. It was and is the result of years of police lynchings carried out in African-American and Latino communities. The fact that an African-American man in his early twenties is twenty-one times more likely to be killed by the police than a white male of the same age was not invented by Sharpton, de Blasio, or the countless grassroots activists who have taken up the battle against police brutality.

It is instead a direct product of a history of white supremacy and unaccountable police departments. Like all lynchings, these murders serve to instill fear and terror in the population, making them normally reluctant to advance demands for justice and progressive change.

The tensions between the police and communities of color are also not in any way new. For instance, the National Negro Congress, a united front organization among African Americans in the 1930s and 1940s, included an end to police brutality as one of its planks.

Third, as horrible and unacceptable as the killing of the two police officers was, black America has endured repeated youth murders at the hands of the police, only to be told that it should exercise restraint, regardless of the circumstances.

Fourth, the movement against police violence has not called for the killings of police. While there are certainly elements who have inappropriate and provocative rhetoric, there is no indication that they have any sizable base or any leadership in the movement. The movement has been militant and active, but it has gone out of its way to advance a nonviolent approach.

While the killing of the police officers was deplorable, there is no basis for a cessation of protests against police violence. This national movement, in point of fact, is actually about much more than police violence. It is about highlighting the continued and growing discrepancies in the treatment of African Americans and Latinos compared with whites.

We must learn critical lessons from the Haymarket massacre and its aftermath. Public opinion can be quickly, and rather easily, manipulated against progressive mass movements in the aftermath of egregious acts. If the movement does not stand strong and pay attention to segments of the population that appear to be wavering in their support for the objectives of the movement, there can be major setbacks.

At the same time, there is nothing inevitable about what happens next. This is why good leadership, organization, and a sophisticated approach to strategy and tactics is so necessary.

I have absolute confidence in the young activists leading today’s movement. I hope that they pay attention to the lessons of history as they continue to battle for justice. They have refocused the attention of much of this country on something that was all but ignored. Now they must press on.

The movement must appreciate that efforts will always be made to discredit it, and to blame the actions of a few on the many. It cannot afford to remain silent or agnostic regarding activities or actions that alienate our base and key supporters and, potentially, isolate the movement itself.

A related point: in making a movement successful, we must pay attention to those in the middle, that is, those who are not as committed to the long-term aims of the movement, but are susceptible to persuasion. The aim is to effectively surround our opponents in such a way that their voice becomes the voice of the discredited minority. When we win over the middle, we have that opportunity.

Finally, winning will involve far more than reforming police behavior. Police lynchings and brutality cannot be viewed in isolation but rather in connection with the existence of a very racially and economically polarized, and increasingly authoritarian, society. The fight against police lynchings is a fight for consistent democracy; a fight that must expand into other arenas including housing, education, jobs, and health care.

Such an expansion will need to be linked not to the resuscitation of the Civil Rights Movement, but rather the construction of a movement for a Third Reconstruction.