A new FBI report finds that the “War on Cops” is real and has deadly consequences.

Undertaken last year after a spate of cop-killings around the nation, the study confirms that areas across the nation have seen “de-policing” in the wake of protests that political leaders seemed to support.

“Law enforcement not only felt that their national political leaders [publicly] stood against them, but also that the politicians’ words and actions signified that disrespect to law enforcement was acceptable in the aftermath of the [Michael] Brown shooting,” the study notes.

“The Assailant Study — Mindsets and Behaviors” examines the men behind 50 cop-killings last year. Most of the perps were simply looking to avoid arrest, but a full 28 percent actively hated police and desired to “kill law enforcement.”

Several, including the killers in Dallas and Baton Rouge, were clearly inspired by the protests that began in Ferguson, Mo.

Nor does the role of movements like Black Lives Matter end there: A number of the killers, the FBI found, were more willing to use deadly force because they believed they were less likely to pay a heavy price for it in the new environment. And, in fact, the study notes that officers across the country report a withdrawal from proactive policing.

In short, the FBI has again proved the Manhattan Institute’s Heather Mac Donald right. She’s spent the last two years describing this dynamic, stating (for example), “Chicago is Exhibit A in what happens when the police back off from enforcing public order, having been told that maintaining control of the streets constitutes racial oppression.”

To be clear, neither Mac Donald nor the study blame everything on Black Lives Matter. Of the 50 cop-killers, 24 were white, 30 had histories of drug abuse and 22 had records of domestic violence.

But the protests, and political sympathy for them, have created an environment where “law enforcement officials believe that defiance and hostility displayed by assailants toward law enforcement appears to be the new norm.”

The study cites an example where an officer was slammed to the ground and beaten, but refused to shoot his attacker “for fear of community backlash.”

“The officer informed the superintendent that the officer chose not to shoot because the officer didn’t want his/her ‘family or department to have to go through the scrutiny the next day on the national news,’ ” the report notes.

New Yorkers are lucky that the NYPD has adapted to the new reality without “de-policing.” The department continues to bring crime down — April was another record month for safety in the city.

But it’s also making ever-stronger efforts to connect beat cops and their commanders with the neighborhoods they protect, to avoid the community hostility that so many police face elsewhere.

That said, the poison can still strike here: In December 2014, an out-of-towner assassinated NYPD officers Wenjian Liu and Rafael Ramos in a lunatic form of “revenge” for the death of Eric Garner.

The anti-cop climate produced by unbalanced media reports and pandering pols means trouble for police everywhere.