The Santa Clara police union is threatening to boycott San Francisco 49ers home games because of Colin Kaepernick’s recent protest of racial injustice and police brutality, NBC Bay Area reported on Friday.

In a letter obtained by the news station, the police union told the NFL team that “police officers [may choose] not to work at your facilities,” if the team did not take action against Kaepernick.

The quarterback refused to stand for the national anthem, in silent protest of police brutality across the US.

Union officers were apparently incensed by that and Kaepernick’s decision to wear socks that depicted a cartoon pig wearing a police hat during practice.

“The board of directors of the Santa Clara Police Officer’s Association has a duty to protect its members and work to make all of their working environments free of harassing behaviour,” the letter added.

The team is standing behind Kaepernick, reiterating an earlier statement that declared, “In respecting such American principles as freedom of religion and freedom of expression, we recognise the right of an individual to choose and participate, or not, in our celebration of the national anthem.”

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