Taking to Twitter on Monday, Stewart -- who is one of many to share his views on the San Francisco 49ers quarterback -- said, "I'm sorry but (Kaepernick) needs to learn the fact about police before running his (expletive) mouth! He has no clue what they go thru!" Stewart completed his tweet with a hashtag and the word "idiot."
Stewart fired back, calling one user an "idiot" as well.
Meanwhile, 49ers legend and Pro Football Hall of Famer Jerry Rice also gave his opinion Monday, disagreeing with Kaepernick's stance.
"All lives matter," Rice tweeted. "So much going on in this world today. Can we all just get along! Colin, I respect your stance but don't disrespect the Flag."
Kaepernick's former head coach, Jim Harbaugh, also spoke out Monday, saying at a Michigan football news conference, "I acknowledge his right to do that, but I don't respect the motivation or the action."
Later, the Wolverines head coach went on Twitter to clarify his remarks.
"I apologize for misspeaking my true sentiments," he said. "To clarify, I support Colin's motivation. It's his method of action that I take exception to."
Rodney Harrison on Kaepernick 'He's not black'
On Tuesday, former NFL player and current NBC football analyst Rodney Harrison caused a stir with his comments on Kaepernick, who is biracial.
"I'll tell you this, I'm a black man, and Colin Kaepernick, he's not black," Harrison said on Sportstalk 790 AM
. "He cannot understand what I face and what other young black men and black people face, or people of color face, on a every single (day) basis. When you walk in a grocery store, and you might have $2,000 or $3,000 in your pocket and you go up in to a Foot Locker and they're looking at you like you about to steal something. I don't think he faces those type of things that we face on a daily basis."
Harrison later backtracked, apologizing on Twitter.
"I never intended to offend anyone," Harrison said. "I was trying to speak about my experiences as (an) African American."
Kareem Abdul-Jabbar: Admire those who risk personal gain
Not all reactions to Kaepernick's protest are negative.
In an op-ed for the Washington Post
, Kareem Abdul-Jabbar
referenced US pole vaulter Sam Kendricks
, who was on his way down the runway at the Rio Olympics. When he heard the national anthem playing, Kendricks, who is a 2nd lieutenant in the Army Reserve, stopped running, put down his pole and stood at attention. He widely was lauded for his nationalism.
But what Kaepernick did, Abdul-Jabbar wrote, is also a sign of patriotism.
"In truth, both men, in their own ways, behaved in a highly patriotic manner that should make all Americans proud," Abdul-Jabbar said.
Abdul-Jabbar goes noted that Kaepernick's stance could negatively impact his career and could potentially cost him millions in endorsements. There's also a chance Kaepernick could be cut from the 49ers, though if that happens, it could be for football reasons rather than social or political ones.
"What should horrify Americans is not Kaepernick's choice to remain seated during the national anthem, but that nearly 50 years after Ali was banned from boxing for his stance and Tommie Smith and John Carlos's raised fists caused public ostracization and numerous death threats, we still need to call attention to the same racial inequities," Abdul-Jabbar said. "Failure to fix this problem is what's really un-American here."
Jim Brown: 'I am with him 100 percent'
Like Abdul-Jabbar, Jim Brown
is no stranger to social activism. He founded the Negro Industrial and Economic Union (later renamed the Black Economic Union) to support black entrepreneurship in the 1960s, as well as the Amer-I-Can program in 1988, an organization dedicated to stopping gang violence and helping individuals "take charge of their lives and achieve their full potential."
The former Cleveland Browns running back and Hall of Famer, appearing on NFL Network's "NFL Total Access,"
agrees with Kaepernick's sentiment, though perhaps not the method.
"I listened to him and he makes all the sense in the world," Brown said. "He's within his rights and he's telling the truth as he sees it. I am with him 100 percent. ... Now if you ask me 'Would I do that?' No I won't, because I see it a little differently. I'm an American citizen, I pay my taxes, I want my equal rights but this is my country, and consequently I don't want to open up for ISIS or anybody that will take away what we've already gained."
Richard Sherman: The 'focus has shifted away from his message'
Seahawks cornerback Richard Sherman, who previously has spoken out about social issues, explained his views on what Kaepernick did.
"You can't ever stand against the flag," Sherman said. "A lot of people have sacrificed for it, but there is also a deeper meaning to what he did. He's talking about the oppression of African-Americans in this country, and that has been going on for a long time. I think a lot of the focus has shifted away from his message. ... I think there's also things in this nation that people need to remember and take heed of and also acknowledge.
"This country is the same country that had 'whites' and 'colored' signs on the bathroom. We're still in that country, we're still in that nation. And that needs to be acknowledged and that needs to be changed. There are people with that mentality that still exists, and that needs to change. There are people that still treat people of color with subjectivity. They treat them a certain way. They categorize them. They put them in a certain category.
"There are certain statistics that are put out there to make sure that police profile certain people in certain neighborhoods, and that needs to change. So there is some depth and some truth to what he's doing.
"I think he could have picked a better platform and a better way to do it, but every day they say athletes are so robotic and do everything by the book. And then when somebody takes a stand like that, he gets his head chopped off."