Police officers and their supporters picket outside Somerville City Hall, Thursday, July 28, 2016, in Somerville, Mass. Somerville Mayor Joe Curtatone is promising not to remove a Black Lives Matter banner from City Hall despite complaints from police officers in the state. (AP Photo/Charles Krupa)
Police officers and their supporters picket outside Somerville City Hall, Thursday, July 28, 2016, in Somerville, Mass. Somerville Mayor Joe Curtatone is promising not to remove a Black Lives Matter banner from City Hall despite complaints from police officers in the state. (AP Photo/Charles Krupa) Credit: Charles Krupa

SOMERVILLE — About 50 police officers and their supporters upset about a Black Lives Matter banner that has been hanging outside City Hall for a year rallied on Thursday to try to pressure the mayor to remove it.

The primarily white opponents of the banner broke into chants of “All lives matter!” and “Take it down!” Many held signs saying “Cops lives matter” and “Support your local police.”

Harold MacGilvray, president of a coalition representing 1,500 officers in 26 communities, said a public building like Somerville’s City Hall is “no place” for political slogans to be displayed.

The mayor of Somerville, a largely white and historically working-class Boston suburb, had earlier in the day promised not to remove the banner despite complaints from officers across the state.

Mayor Joe Curtatone, a white Democrat, said Thursday afternoon it’s “OK to disagree” and the only way to resolve the impasse is through an “open dialogue” about race.

“That sign is not coming down,” he insisted while standing in front of City Hall flanked by the police chief and two deputy chiefs.

The Somerville Police Employees Association was among the unions represented at the opposition rally Thursday evening outside City Hall. Its president, Michael McGrath, said his officers support the “core goal” of the Black Lives Matter movement but believe the banner sends an “exclusionary message” and is disrespectful to officers.

“In the face of the continuing assassination of innocent police officers across the country … it is irresponsible of the city to publicly declare support for the lives of one sector of our population to the exclusion of others,” McGrath said in a statement this week.

As the police rally was breaking up, some Black Lives Matter supporters held signs saying “All lives can’t matter until black lives matter” or thanking the mayor for his stand.

Curtatone, the son of Italian immigrants and the mayor since 2004, has argued that standing up for minority residents and supporting police aren’t “competing interests.” He noted the city has hung a banner over police headquarters honoring officers slain in Dallas and in Baton Rouge, La.

“Both of those banners are hanging for the same reason: Too many people have died in a cycle of violence that needs to be stopped,” he said in a statement.

When asked whether he thought it was appropriate to place the Black Lives Matter banner on a government building, he replied: “No one can sit out this conversation. Where this is happening is in cities. This is the grassroots level.”