Supporters of the New York Police Department have risen up in anger against the unlikely target of Chipotle burrito chefs, thanks to a viral Facebook post that alleged employees of the fast-food chain refused service to eight officers – and despite the chain’s rebuttal of the details contained in the post.

Chipotle’s involuntary participation in the racially charged debate over police behaviour gripping New York began on 17 December, when Ray Melendez, a Brooklyn resident who identified himself as a former NYPD officer, wrote on Facebook – in a post that was deleted on Monday – that “an officer involved at the incident” told him several employees of a local Chipotle had “raised their hands & said: ‘Hands Up, Don’t Shoot’ to the officers”.

Melendez said the officers “simply left the location without any further action at the scene rather than provoke what could be a losing situation, given the climate of ‘support’ from our Mayor”. Many members of the NYPD have denounced the mayor, Bill de Blasio, for what they perceive as his support for recent protests over police killings of unarmed black men.

Melendez then quoted a complaint by another former NYPD officer, Scott Lothrop, who said the “familiar but completely erroneous ‘Hands Up, Don’t Shoot’ gesture” caused the on-duty officers “a great deal of embarrassment, annoyance and humiliation”.

Lothrop said he would boycott Chipotle for the staff members’ “unconscionable” gesture, which he said was made at a time when “race baiting anarchists [are] descending on New York”.

Descriptions of the incident, reworded and including the new assertion that employees had refused the officers service, then took off online. Pro-police and pro-protest commenters seized on it, adding their own vitriol, outrage and hysteria. Conservatives demanded a boycott of Chipotle and the termination of the “anti-NYPD employee”; liberals appended the hashtag #BlackLivesMatter and mocked conservative outrage.

Chipotle’s communications director, Chris Arnold, sent the Guardian the company’s report of the incident, which was made after a review of surveillance footage and interviews with the location’s employees. Arnold said that on 16 December, nine police officers entered the Brooklyn restaurant and saw one of its employees “raise their hands in what appears to have been a gesture of protest directed toward the NYPD”.

Arnold’s statement said the investigation found the gesture “appears to have been a spontaneous, unplanned action taken by an individual crew member and was not a coordinated effort by the staff”. Chipotle’s version of events falls in line with Melendez’ original post, saying that the officers were not refused service but voluntarily left the restaurant.

Chipotle management took “appropriate actions” with regard to the employee who made the gesture. Arnold declined to say what that meant, citing privacy concerns.

As for Chipotle’s position in the heated conversation about race and policing, Arnold made clear the company’s focus is on getting tacos, rather than race issues, on customers’ minds. The chain’s statement distances itself from the gesture by saying it “undermined” the company’s policy that employees treat customers with respect.

Finally, chief executives Montgomery Moran and Steve Ells said in a statement that Chipotle apologises to the officers involved and to “many of the people who have contacted us”.

“We have proudly served law enforcement officers … around the country for the last 21 years and we continue to do so every day,” Moran and Ells wrote. “We greatly respect the service they provide and welcome them into our restaurants.”

Melendez’s post, however, continues to live a life of its own, coloring Chipotle reviews and fueling partisan talking points.

Protests against police erupted around the US after the killings of several unarmed black men, including Michael Brown in Ferguson, Missouri, and Eric Garner in New York. None of the officers involved have been indicted, provoking greater outrage.

The focus has most recently landed squarely on the NYPD, which lost two officers after a man shot them dead as they sat in their patrol car. The gunman, Ismaaiyl Brinsley, who also shot and wounded his ex-girlfriend, was reportedly motivated by hatred for the police.

On Saturday, officers turned their backs on the mayor during a funeral for one of the officers. Pat Lynch, the head of the city’s main police union, said many police felt “betrayed” by the mayor and the public.

On Monday, De Blasio was greeted by some booing and heckling when he spoke at a ceremony for graduates of the New York Police Academy.