"We all have an obligation no matter the risk, and regardless of reward, to stand up for our fellow men and women who are being oppressed with the understanding that human rights cannot be compromised," Kaepernick said at the event, making a rare public comment, per CNN.com's Jill Martin.
Kaepernick, 30, has remained a free agent during the 2017 NFL season despite throwing for 2,241 yards and 16 touchdowns against four interceptions in 2016. He's filed a lawsuit against the NFL, claiming the league's ownership colluded to keep him unsigned due to his protest of systemic racism during the national anthem.
"He has lost his job, one that he loved and was supremely talented and skilled at," Hector Villagra, executive director of the ACLU of Southern California, told the crowd of supporters. "He took a stand knowing that some would criticize him, and he has been viciously and unfairly criticized. He has been called a traitor because too many people in this country confuse dissent for disloyalty."
Kaepernick's name has remained at the forefront of conversations around the NFL. President Donald Trump, who has vehemently criticized protests during the national anthem, said the NFL should have suspended Kaepernick last year to quell the demonstrations.
"The NFL should have suspended him for one game and he would have never done it again," Trump told Fox News' Sean Hannity in October. "They could have then suspended him for two games and they could have suspended him again if he did it a third time, for the season, and you would never have had a problem."
Kaepernick and his work on social issues have been lauded in many other circles. He was named GQ's "Citizen of the Year" last month.
"My goal this year has been to get the narrative back on track," former 49ers teammate Eric Reid, the first player to join Kaepernick protesting, told GQ. "We started having communications with the NFL, and they said they're going to help us make progress on these issues. But the next step is to get Colin back in the NFL. Because he's the one that started this. I think we're finally getting where me and Colin envision this going. Now it's time for him to get back in the league.
"These issues are real, and people know they're real. But some will do anything to distract from that, to change the narrative, and it's gotten Colin blackballed from the NFL."
Kaepernick has not received significant consideration from any team during the regular season.