SOMERVILLE (CBS) – The Somerville Police Employees Association wants Mayor Joseph Curtatone to take down a Black Lives Matter banner at city hall.

The officers’ union wants it replaced with a banner that says All Lives Matter.

Read: The Letter

In a letter to Curtatone Tuesday, the association said they are “deeply troubled” by the mayor’s decision to display the banner, while “standing silent over the seemingly daily protest assassinations of innocent police officers around the country.”

The banner has been hanging outside city hall since August 2015.

The letter, signed by the group’s president Michael McGrath, says:

“The Somerville Police Employees Association fully endorses the proposition that black lives matter just as much as white, Asian, and Hispanic, and any others do. Similarly, we respect the rights of all American citizens, including those well-intentioned members of the BLM movement, to protest injustice.”

“At the same time, we strongly object to a public banner sponsored by the City that impliedly paints police officers as the killers of innocent citizens of color when there is no evidence whatsoever that the police officers in the City are in anyway using their police powers in a discriminatory or unlawful way.”

The letter was written unbeknownst to Somerville Police Chief David Fallon, who said he’d prefer to keep politics out of policing.

“If you want to talk national issues and what’s going on, there needs to be more dialogue, not an open letter to the Mayor,” said Fallon.

In a statement, Curtatone said the banner will stay. He noted that a banner hanging at the police station honoring officers killed in the line of duty in Dallas showed Somerville’s support for police.

“My unwavering support for our police officers does not and cannot preempt our commitment to addressing systemic racism in our nation,” Curtatone said.

“The City of Somerville stands against all violence and all injustice, which is why a Black Lives Matter banner hangs at City Hall and why a banner in honor of the slain officers is hanging at Somerville Police Headquarters where it would provide the most moral support to our officers—both on my order. Both banners will remain hanging.”

“I know the mayor, I know he doesn’t like being told he’s wrong, doesn’t like being questioned,” McGrath told the Boston Herald.

WBZ NewsRadio 1030’s Ben Parker reports