Colin Kaepernick's decision to protest the national anthem on Friday has become a lightning rod of controversy around the NFL over the past two days.

While some players have come out in support of Kaepernick and his right to protest, other players are livid with Kaepernick, including one of his ex-teammates.

Vikings offensive lineman Alex Boone, who spent five seasons as Kaepernick's teammate in San Francisco, says that the 49ers quarterback needs to show some "f------ respect."

"It's hard for me, because my brother was a Marine, and he lost a lot of friends over there," Boone said, via USA Today. "That flag obviously gives (Kaepernick) the right to do whatever he wants. I understand it. At the same time, you should have some f------ respect for people who served, especially people that lost their life to protect our freedom. And I get that he can do whatever he wants. But there's a time and a place. Show some respect, and that's just how I feel."

Boone also called it shameful that Kaepenick didn't stand.

"You see all these pictures of these veterans that have no legs, and they're standing up in a wheelchair," Boone said. "I had a brother that served, and he lost friends, and I know how much it means to him. It's shameful."

Boone's brother J.J. is a marine who once served in Iraq.

"We're out here playing a game, making millions of dollars," Boone said. "People are losing their lives, and you don't have the common courtesy to do that. That just drove me nuts."

The only reason Boone wasn't more upset with Kaepernick is because the Vikings lineman had heard about the comments that Anquan Boldin made about the situation.

"Anquan said it this morning [that Kaepernick had the right to do it], and I was kind of mad that he said it, because I was like, 'God, if Anquan says it, I've got to go with it,' because Anquan was such a leader, and he's a smart guy. He gets it," Boone said, via ESPN.com. "But at the same time, I was upset with his choice to do that and kind of disrespect the flag."

Boldin, who played for the 49ers from 2013-15, said that he has no issue with the fact that Kaepernick was protesting the national anthem because living in America gives them that right.

"I respect everybody's opinion," Boldin said, via the Detroit Free Press. "Everybody has one. I'm sure he's going to get flack for it, what he did, but that's the great thing about being in America, you have that option."

Boldin and Boone are a good example of the divide in opinion that Kaepernick's actions have created across the NFL. Coaches and players have been coming out on both sides of the issue ever since Friday when Kaepernick decided not to stand for the national anthem.

Kaepernick has said that he's going to continue to sit until there is "significant change and I feel like that flag represents what it's supposed to represent in this country ... I'll stand," which means this is an issue that's likely only going to get bigger and bigger as long as he remains on an NFL roster.