Across the country, billboards are springing up in a show of support for law enforcement, marked with the message "Blue Lives Matter." And though the advertising firms behind them say they've received positive feedback, Black rights advocates argue that "Blue Lives Matter" was copied from "Black Lives Matter" for the wrong reasons.

Tactical Magic, a Memphis-based advertisement firm, launched the pro-cop campaign last month in response to growing criticism of police, and now other agencies are following suit. Lamar Advertising, based in Baton Rouge, Louisiana, already donated 150 of its digital billboard spaces to the campaign.

"I think in some aspects it's shameful that the brand is being co-opted, but once again it was never meant to say 'only Black Lives Matter,'" Darel Ross, co-executive director of LINC Community Revitalization, told a Fox affiliate network.

"Black lives matter was simply to call attention to a unique set of circumstances that was happening in the black community; and to any way undermine that, or belittle that, ultimately in no way shape or form adds to the relationship between police officers and the Black community, or the community at large, because most people get it."

Following the fatal, police-involved shooting of Michael Brown last year, the Black Lives Matter movement quickly spread in the U.S., highlighting problems of racial injustice and advocating against police brutality. By using the a modified version of the Black rights motto, these billboards have drawn criticism online for appearing indifferent to the movement's concerns.

"The idea initially was to salute those men and women who serve us in law enforcement," Tactical Magic creative director Trace Hallowell said in a press release. "This time the message was simply to affirm the humanity of our men and women in uniform. No one should be a target of violence because of what they wear."

Since the advertising campaign started, the digital billboards have appeared everywhere from Ohio to Oregon, leading supporters to post them online with the hashtag #thankublu.

Lamar Advertising said it plans to add another 100 boards to its fleet by the first week of November.