Dan Berger is an associate professor of comparative ethnic studies at the University of Washington Bothell and the author of "Captive Nation: Black Prison Organizing in the Civil Rights Era," among other titles.

White nationalist demonstrators walk into the entrance of Emancipation Park surrounded by counter demonstrators in Charlottesville, Va. (Steve Helber/AP)

Klansmen, neo-Nazis and other assorted white nationalists described their descent on Charlottesville as a gathering to “Unite the Right.” Its bloody end, when one of them drove his car into a cluster of counter-demonstrators, killing one and injuring 19, was no aberration. Rather, murderous violence has been the through-line connecting four decades of efforts at uniting America’s far right. And such efforts have had a shocking amount of support from sectors of the U.S. government committed to “law and order.” Whether from law enforcement officials or the president, such support legitimizes the otherwise fringe politics of white nationalism and facilitates more racist attacks.

Law enforcement has been at the heart of the government’s uneasy relationship with white supremacist groups since the 1960s. Alabama Sheriff Eugene “Bull” Connor is but the most infamous in a long line of blustery law enforcement officials who aided violent attacks on black communities and left-wing activists. While Connor incited segregationist mobs to act, other police officers merely turned away when they did.

It was not just Southern sheriffs, either. For years, J. Edgar Hoover refused to act to prevent attacks on civil rights activists when his informants warned him such assaults were imminent. Worse still: FBI informants participated in such attacks. Gary Thomas Rowe was a paid informant for the FBI when he rode along with the carload of people who shot and killed activist Viola Liuzzo, a white mother of five from Detroit who had traveled to Selma in support of the civil rights demonstrations there. After her death, the FBI director tried to discredit her by telling President Lyndon Johnson and Attorney General Nicholas Katzenbach that Liuzzo had “indications of needle marks in her arms” and “was sitting very, very close to the Negro in the car” she was traveling in when the Klan attacked her.

Law enforcement’s complicity in the affairs of right-wing insurgents overlapped with dangerous developments on the right. Throughout the 1970s, the Klan grew closer to neo-Nazi groups in both ideology and strategy. While earlier iterations of the Klan had fashioned themselves as defenders of an old world order, the new Klan had a more expansive vision — one that anticipated the ideology of the alt-right today.

More than keeping blacks or Jews “in their place” through violence, the new Klan channeled the Nazi idea of an Aryan ethnostate, purged of all enemies. And it upped its commitment to militarism. The newly merged neo-Nazi and Klan groups stockpiled weapons, studied torture techniques and declared the U.S. government as well as African Americans, Jews, gays and lesbians and leftists as enemies of their white nationalist fantasies.

One of the first indicators of this newly unified right could be seen in Greensboro, N.C., in 1979. Before then, Greensboro was perhaps best known for its contribution to the civil rights movement: It was there that four black students from North Carolina Agricultural and Technical State University launched a spontaneous sit-in at a segregated lunch counter on Feb. 1, 1960. Their actions rippled across the South. By the end of the month, there were more than 30 sit-ins in seven states.

Yet the sit-ins were a distant memory in 1979, when North Carolina saw a growth in right-wing paramilitary groups. In response, a new brash left-wing group called the Communist Workers Party organized a march against the Klan. They called their rally “Death to the Klan” and even dared the “two-bit punks” to show up.

But it was not the Klan who died that day. Calling itself the United Racist Front, a caravan of Klansmen and neo-Nazi groups from throughout the state descended on the rally. The men parked their cars, calmly removed weapons from their vehicle trunks and opened fire.

Newscasters captured 88 seconds of carnage as armed racists gunned people down in the street. When they stopped firing, five leftists lay dead: Cesar Cauce, Michael Nathan, William Sampson, Sandra Smith and James Michael Waller. In their 20s and 30s, the dead were union organizers, doctors and committed antifascists. Another 12 people were wounded, some paralyzed for life.

Subsequent investigations revealed how thoroughly involved police agents were in what became known as the “Greensboro massacre.” Two paid police informants were involved in planning the attack, while others refused to intervene to stop the imminent bloodshed. One of the informants, Klansmen Eddie Dawson, played an instrumental role in partnering with the neo-Nazi National Socialist Party of America. Dawson also led the caravan that attacked the demonstrators.

The local police department knew of Dawson’s role and the likelihood for violence. Yet according to the 2006 report by the Greensboro Truth and Reconciliation Commission, police did not warn demonstrators that the white supremacists planned to attack them. Police officials directed their officers to stay away from the rally and not intervene before, during or after the attack. The Bureau of Alcohol, Tobacco and Firearms and the FBI had been monitoring the neo-Nazi groups but also declined to intervene. In fact, the ATF had their own informant in the neo-Nazi group who participated in planning the attack.

Nearly 40 years later, the macabre ghost of the Greensboro massacre haunts us still. While there is no evidence of police participation in the Unite the Right rally, several commentators report that police refrained from confronting the white nationalists. President Trump has not only defended the right-wing demonstrators but also taken up their cause as well, protesting the removal of Confederate statues and praising the Confederacy through a host of fictitious and distorted claims.

Yet the sagacious ghost of the Greensboro sit-ins of 1960 also remains and provides an example of the principled courage needed to confront the racism of white nationalists in and out of government. Two days after Heather Heyer’s killing, a group of demonstrators — seven of whom now face felony charges — took down the Confederate Soldiers Monument at the Durham County Courthouse in North Carolina. It was one of several of anti-racist demonstrations nationwide against the right-wing violence that took Heyer’s life.

Much as the civil rights movement took bold action to topple Jim Crow, today’s demonstrators are once again taking direct action against government and local law enforcement officials, as well as the white nationalists they protect, to force them to decide whether they stand for justice or racial violence.