NASCAR driver Tony Stewart called NFL quarterback Colin Kaepernick an “idiot” and “dumbass” for his decision to sit down during The Star-Spangled Banner in an attempt to protest perceived racial injustice.

Stewart called out the San Francisco 49ers quarterback on Twitter on Monday, saying the 28-year-old Kaepernick is wrong in his perception of law enforcement.

“I’m sorry but @Kaepernick7 needs to learn the fact about police before running his dumbass mouth! He has no clue what they go thru! #idiot,” Stewart wrote.

Stewart then responded to several users who questioned his initial take, including one person, @DaSportsSavant, who asked “do you know what Black people in poverty go thru?”

“I honestly don’t. But I know plenty of officers. And I know if they weren’t there it would be worse there,” Stewart wrote.

Stewart later sought to clarify his comments: “For the record, I’m not saying our nation isn’t messed up, just that police officers are not the root of the problem. They take the blame.”

Miami Dolphins running back Arian Foster, who has been supportive of Kaepernick’s stance, tweeted that Stewart should have directly addressed Kaepernick with any concerns.

“how about attempting to educate him via your views instead of fueling hatred. You can get ahold of him if you want,” Foster tweeted.

Stewart hadn’t responded to Foster as of Tuesday afternoon.