Josina Anderson says the people who came out to back Colin Kaepernick were given courage from the recent events in Charlottesville, Virginia, and Boston. (2:14)

NEW YORK -- Supporters of former San Francisco 49ers quarterback Colin Kaepernick, who refused to stand for the national anthem to protest police brutality against black people, showed their solidarity with him and his cause at a rally outside NFL headquarters Wednesday, demanding that he be signed by the start of the regular season next month.

More than 1,000 people, many wearing jerseys bearing Kaepernick's name, crowded the steps outside the NFL's midtown Manhattan offices.

Kaepernick, who once took the 49ers to the Super Bowl, opted out of his contract with the team in March and remains unsigned. Supporters say he is being blackballed for his advocacy, but some critics say he should not have sat or kneeled during the anthem or contend his lack of a job is more about his on-field talent. Kaepernick led the 49ers to a 3-16 record the past two seasons.

Chants at the demonstration included "Boycott! Boycott!''

Women's March organizer Tamika Mallory, addressing football fans, said, "I don't care how long you've been watching football, if they don't stand up for your children, turn the damn TV off."

Some speakers said the league's treatment of Kaepernick is of a piece with a cavalier attitude toward players' health.

"How in the world can we call ourselves the land of the free, the home of the brave, and you get vilified and criminalized just for speaking your mind?'' the Rev. Jamal Bryant said. "The NFL has proven with their treatment of Colin Kaepernick that they do not mind if black players get a concussion. They just got a problem if black players get a conscience."

More than 1,000 people attended a rally in front of the NFL's offices in New York in support of unsigned quarterback Colin Kaepernick. Drew Angerer/Getty Images

Earlier Wednesday, the NAACP called for a meeting with the NFL to discuss the fate of Kaepernick, who was born to a white woman and a black man but was adopted by a white couple. The civil rights organization's interim president, Derrick Johnson, said in a letter to NFL commissioner Roger Goodell that it's apparently "no sheer coincidence'' that Kaepernick isn't on a roster.

"No player should be victimized and discriminated against because of his exercise of free speech,'' Johnson said. "To do so is in violation of his rights under the Constitution and the NFL's own regulations."

ESPN Staff Writer The Colin Kaepernick rally concluded after about an hour and a half of speeches, poems and prayers. Hard to tell how many people were outside the NFL headquarters in NYC, but suffice to say it was a lot more than the approximately 70 who showed up in the first rally back in late May.

The NAACP's state president in New York, Hazel Dukes, said: "Right now, the action of the league seems to imply to young black men that this league, which is comprised of 70 percent African-Americans, only values black lives if they are wearing a football uniform."

Goodell has said the league isn't blackballing Kaepernick.

Some other players followed Kaepernick's actions last season, and some are doing so in this year's preseason. On Monday, a group of Cleveland Browns players prayed in silent protest during the national anthem. Among those kneeling was a white player, Seth DeValve. Another white player, Britton Colquitt, did not kneel but kept his hand on the shoulder of a teammate who did.

That protest earned the ire of an Ohio Supreme Court justice, the lone Democrat holding an Ohio statewide office. Justice Bill O'Neill wrote on Facebook that he wouldn't attend any games at which "draft dodging millionaire athletes disrespect the veterans who earned them the right to be on that field."

"Shame on you all,'' he said.