Aaron Lewis's strong opinions don't end with country music. The singer says he's infuriated that NFL quarterback Colin Kaepernick doesn't stand during the National Anthem, and he's even more upset that the league lets it happen.

During an interview with Radio.com, Lewis said he was even more angry at the NFL for allowing the player to not stand when the anthem is played pre-game. The San Francisco 49er backup quarterback has been a polarizing figure since he first sat during the ceremony in a pre-season game. Other NFL players have now joined him in some sort of protest, be it kneeling, holding hands or raising a fist.

"I am not going to stand up to show pride in a flag for a country that oppresses black people and people of color," Kaepernick said at the time.

"They're not benching him," Lewis points out explaining his ire, "they're not financially penalizing him every time he doesn't stand. That is a direct slap against he country that makes the NFL as great as it is."

Lewis recently notched the No. 1 album in country music with Sinner. The project has been praised for it's dedication to traditional country, but it too is not without opinions. A single called "That Ain't Country" takes aim at modern country music, something Lewis has done on and off stage. At a recent show he called out artists like Luke Bryan and Sam Hunt for "choking all the life out of country music."

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Watch: Aaron Lewis Blasts Modern Country Music