Before an NFL preseason game last week, San Francisco 49ers quarterback Colin Kaepernick refused to stand for the national anthem. When asked why, he said he wouldn’t “show pride in a flag for a country that oppresses black people and people of color.”

The backlash began almost immediately.

One fan burned Kaepernick’s jersey as the national anthem sounded in the background. Minnesota Vikings guard Alex Boone excoriated Kaepernick for not showing “respect for people who served, especially people that lost their life to protect our freedom.” Tennis star John Isner called Kaepernick’s actions “pathetic” and said, “I’m a big Blaine Gabbert fan now,” referring to the 49ers quarterback Kaepernick is jostling with for the first-string position. Donald Trump said Kaepernick “should find a country that works better for him.” Sports journalist Clay Travis labeled the Niners quarterback a “fucking idiot.”