Social media was abuzz late on Saturday over the controversy surrounding American football player Colin Kaepernick's refusal to stand during the US national anthem. The quarterback for the San Francisco 49ers of the National Football League (NFL) has said his decision was a form of protest against racial injustice in the country.

"I am not going to stand up to show pride in a flag for a country that oppresses black people and people of color," said Kaepernick. As he took to the field on Thursday's preseason game against the Green Bay Packers, fans booed the quarterback who once led their team to its last Super Bowl appearance in 2013.

No stranger to racial politics

Kaepernick is the son of a white mother and black father, but was adopted by a white couple from Wisconsin as an infant. He has spoken openly about the struggle he faced growing up as a mixed-race child in a mostly white community.

"I knew I was different to my parents and my older brother and sister," he said once in an interview, adding that strangers often didn't believe he belonged with his family.

The 49ers organization stood behind their quarterback in responding to the controversy, saying that "we recognize the right of an individual to choose and participate, or not, in our celebration of the national anthem."

Many fans and fellow athletes were not as forgiving. One video that went viral on Facebook showed a 49ers fan setting fire to his Kaepernick jersey. Others have criticized Kaepernick for not appreciating a nation where he was able to become a millionaire in the span of just a few years, and for what they saw as disrespecting the soldiers who risk their lives fighting for the US, a huge taboo in the country.

Other NFL players, such as Green Bay Packers quarterback Matthew Hasselbeck, have condemned Kaepernick's actions in no uncertain terms:

And Justin Pugh of the New York Giants:

Another line of argument emerged on social media, however, suggesting that those who slammed Kaepernick illustrated how little tolerance there is the US for anyone in the public eye to voice criticism of the country.

This was not the first time Kaepernick has been caught in the middle of America's charged racial politics. When he was made the 49ers starting quarterback in 2012, Sporting News, one of the oldest sports news publications in the US, compared the star's multiple tattoos to the prevalence of tattoos amongst prison inmates.

Kaepernick took the comment in stride, however, saying an outright questioning of his stylistic choices was preferable to the vaguely racist questions he was regularly asked in interviews. In the past few years, he has often been vocal about racial conflict and is strong defender of the Black Lives Matter movement.

"To me, this is bigger than football and it would be selfish on my part to look the other way," Kaepernick told NFL media.

"I am not looking for approval. I have to stand up for people that are oppressed... If they take football away, my endorsements from me, I know that I stood up for what is right."