Mark Schiefelbein/Associated Press

President Barack Obama described Colin Kaepernick's national anthem protest as "messy" but said Monday he supports the San Francisco 49ers quarterback's constitutional right to protest.

"I don't doubt his sincerity," Obama said. "I think he cares about some real, legitimate issues that need to be talked about, and, if nothing else, what he's done is generated more conversation about some topics that need to be talked about."

The president, speaking at the G20 economic summit in China, said he has not paid close attention to the issue that's overtaken the NFL news cycle.

Kaepernick sat or knelt down while the national anthem was playing throughout the preseason as an act of protest of discrimination against people of color. The decision did not make national news until after the 49ers' third preseason game, when a reporter asked him to discuss the matter.

The QB said the following, per Nick Wagoner of ESPN.com:

People don't realize what's really going on in this country. There are a lot of things that are going on that are unjust. People aren't being held accountable for. And that's something that needs to change. That's something that this country stands for freedom, liberty and justice for all. And it's not happening for all right now.

President Obama acknowledged that some members of the military or law enforcement may feel slighted by Kaepernick's actions. Chief Michael J. Sellers of the Santa Clara Police Department issued a statement over the weekend acknowledging that his department may choose not to work security at 49ers games if the team "[does] not address his behavior."

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The president nonetheless took a supportive, albeit neutral, stance on the matter.

"I'd rather have young people who are engaged in the argument and trying to think through how they can be part of our democratic process than people who are just sitting on the sidelines not paying attention at all," he said.

Teammate Eric Reid and Seattle Seahawks cornerback Jeremy Lane have since joined Kaepernick. United States women's national soccer team star Megan Rapinoe joined the protest Sunday night, taking a knee when the national anthem played prior to her NWSL game.

"I am disgusted with the way he has been treated and the fans and hatred he has received in all of this," Rapinoe told espnW's Julie Foudy. "It is overtly racist. 'Stay in your place, black man.' Just didn't feel right to me. We need a more substantive conversation around race relations and the way people of color are treated."

Others, such as New York Giants offensive guard Justin Pugh, have been openly critical of Kaepernick and have made it a point to say they would continue standing.

The 49ers organization has publicly supported Kaepernick and retained him on the 53-man roster despite some speculation he could be released.

Follow Tyler Conway (@jtylerconway) on Twitter.