Colin Kaepernick (7) kneels during the national anthem before a game against the Bills. (Mike Groll/AP)

Sunday was decidedly up-and-down for the 49ers’ Colin Kaepernick, who didn’t play particularly well in a 45-16 loss to the Bills but who had to be delighted to be making his first start since last November. A similar dynamic unfolded off the field, as many in the Buffalo crowd showed great antipathy for the quarterback’s national-anthem protests, while others expressed support.

After the game, Kaepernick was asked about his reception, which included loud booing when he took the field for warmups in Orchard Park, N.Y., as well as chants of “U-S-A!” just before the national anthem. As he has been doing since preseason games in August, the 28-year-old Wisconsin native knelt during “The Star-Spangled Banner” to display his concern with racial injustice, particularly involving the treatment of black men by police.

“I don’t understand what’s un-American about fighting for liberty and justice for everybody, for the equality this country says it stands for,” Kaepernick told reporters. “To me, I see it as very patriotic and American to uphold the United States to the standards that it says it lives by.”

Asked about a report that a Bills fan had hurled a bottle  of beer at him, Kaepernick responded with a chuckle, saying, “If they did, they didn’t have very good aim.

“But I had some Bills fans before the game come up and say they are supporting me, so I think it all depends on who the person is,” the quarterback continued. “But, you know, at the end of the day, I’m going to continue to fight for what I’m fighting for.”

Some Bills fans marched outside the stadium in support of Kaepernick before the game, and they also participated in a “kneel-in.” One of them told the Huffington Post, “We had been talking about doing this for a while even before we found out he was starting. We want to show that we support him because what he’s doing is very patriotic, and as Bills fans, we stand for racial justice.”

“That’s huge,” Kaepernick said of his fellow protesters Sunday (via ESPN). “I think it’s something that, once again, people are realizing that these are real issues that affect many people. It’s something that has to be addressed. Until us as people recognize and address that some of us have privilege, some of us don’t and some of us are able to do certain things without consequences and others of us can’t. Those are all things that need to be addressed.

“Me as a black man that plays football and is considered a celebrity, I’m treated differently than a black man that’s working 9 to 5 in the ‘hood,” he added. “That’s just the reality of it. It shouldn’t be that I’m treated differently than that person or he’s treated differently than me. We’re human beings, and it should be something that everybody is treated that way.”

As for Kaepernick’s in-game performance, he completed 13 of 29 passes for 187 yards, one touchdown and no interceptions, adding 66 yards on eight carries. Coach Chip Kelly, when asked if Kaepernick would continue to be the 49ers’ starter, would only say, “We’ll see,” but there’s no doubt that the quarterback’s anthem protests will continue, as will the disagreement over whether they constitute acts of patriotism or something less admirable.