The most pivotal moment in Ezra Edelman's breathtaking documentary O.J.: Made in America, the moment that affects every scene afterward, the moment that lays down what's at stake and why all of that mattered, is not when O.J. wins the Heisman Trophy. It's not when he becomes a Hertz pitchman and one of the most recognized people on the planet. It's not even the murders.

No, the moment that changes everything comes when O.J. has emerged as the next great athletic hero at USC at the exact time the American civil rights movement is blossoming. Black sports stars like Muhammad Ali, Jim Brown, Kareem Abdul-Jabbar and Bill Russell saw what was happening in the world around them and decided that they could not stand idly by. They banded together and held press conferences and spoke openly and angrily about the plight of black men and women in the United States. These were men in the primes of their careers. Ali was the heavyweight champion; Abdul-Jabbar was dominating college basketball as Lew Alcindor; Russell had won his fifth NBA MVP award; Brown had led the NFL in rushing eight of nine seasons before retiring to pursue his acting career. These were men with a ton on the line. And they were willing to risk it all for a cause they believed in.

Not everyone did, including, famously, O.J., who said, "What I'm doing is not for principles or for black people. I'm dealing first for O.J. Simpson, his wife and his baby." This is not an insane thought. Life is difficult enough, and O.J., who was in college, decided not to make his life more difficult by signing on for a cause that would cost him millions and potentially stand in the way of everything he was working for. Everybody has to make his or her own decisions. That was his.

In Edelman's documentary, this is the moment that changes everything for O.J. He leaves one community behind for another, with perilous results. Edelman's focus on the Ali/Brown/Abdul-Jabbar/Russell contingent shows that Ali and company drew a line in the sand: You are either with us, or you are not with us, and there is no middle ground. Simpson would have loved to spend his whole life not being asked about civil rights issues. Ali and his consortium assured that would not be possible. You cannot dance between the raindrops forever.

Watching the film earlier this year, I was taken aback by this moment and, particularly, how there was no real modern-day equivalent. How, since then, there hadn't been anyone nearly as high-profile as those athletes taking a stand on the issue of civil rights, a hill they were willing to die on. What did Michael Jordan think about life in the United States for African-Americans? Rickey Henderson? Barry Sanders? Ken Griffey Jr.? Kobe Bryant? Tiger Woods? They never had to say anything. No one ever put them in the position that Ali put Simpson in. There were socially conscious athletes, sure, from the Suns wearing their "Los Suns" jerseys to protest Arizona's anti-immigration law to the Clippers wearing their warm-up jerseys inside out in the midst of Donald Sterling's madness to Tavon Austin making the "hands up, don't shoot" gesture to the Miami Heat responding to the death of Trayvon Martin.

But, as courageous of some of those were, they didn't really put too much on the line. LeBron put up a tweet; Austin briefly flashed a hand signal; the Suns and the Clippers briefly changed clothes. This is not to devalue their messages or their willingness to take a stand; it is just to say that the public discord they risked was minimal. As long as they kept dunking and scoring touchdowns, no one was going to stop cheering for them or buying their merchandise. They were not press conferences in which the top sports stars on earth openly challenged what they believed to be a racist power structure. All their statements came with an approving Nike swoosh.

Now, however, with Colin Kaepernick, we have something very different.

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Lost in the debate on Saturday in the wake of Colin Kaepernick's comments that he refused to stand for the national anthem before Friday's 49ers preseason game because, he told NFL Media, "I am not going to stand up to show pride in a flag for a country that oppresses black people and people of color," is that now there is a line drawn in the sand.

This is a story that is not going to go away. It is one thing to wear a hoodie. It is another thing to, as an NFL player no less (a league that, remember, has actually received money from the military to stage its on-field tributes), say, "I am not standing up for the national anthem because of how African-Americans are treated in this country." The backlash has already been immense, and it is only beginning. The culture of the NFL is so ingrained -- and the racial makeup of fans in the stands so cemented -- that Kaepernick is going to get massive boos every time he touches the ball, probably for the rest of his career. There is a presidential election coming up that is more racially polarized than any in several decades, including ones that included an African-American candidate; there is zero chance isn't commented on by one or both candidates in the coming days. (It's already dominating cable news.) In this environment, it instantly becomes of the major storylines of the NFL season. This is a pivotal moment.

Kaepernick said he understood what he was walking into by making this statement. We shall see. Because it's going to be brutal. It's already brutal. (Saturday might have been the most "get off the internet and go outside so you don't lose faith in humanity" day in recent memory.) There are literally hundreds of millions of people who disagree with Kaepernick not standing for the national anthem. There are defenders of his who disagree with him on this. (Bleacher Report's Mike Freeman has probably been the best journalist on this story since it broke.) His union chief disagrees with him on this. I disagree with him on this; I believe standing for the national anthem is a way to honor the principles the flag stands for, even if (especially if) those principles are being trampled on in practice by us flawed, stupid humans. But that does not mean his reason for doing so is inherently wrong. And the idea that the team, or the league, should do something about Kaepernick's stance, that it shows he's somehow "ungrateful," is exactly the opposite of what the flag is supposed to stand for.

But if you don't think Kaepernick isn't onto something foundational in the league's power structure, or for that matter the country's …

Kaepernick got everyone's attention focused on the issues he cares about not by doing something modest that many people will agree with him on, but by doing something that invites loud disagreement. He has been talking on his Twitter feed about African-American oppression for months, and few have even noticed. (He has also heavily criticized Hillary Clinton on his Twitter feed, by the way.) They have noticed now. That was the point of this. You can disagree on the anthem stance, but Kaepernick has forced his issues into the public conversation. That's a lot to put on one's back. He has legitimately risked something; he has legitimately risked everything. That is something we have not seen in a long time.

And it's what happens next that matters. Over the next week, every major black athlete in this country is going to be asked what they think of Kaepernick's protests. (Fewer white people will be asked, though one suspects it will not slow the flow of opinions. It didn't stop mine!) Cam Newton will be asked. Russell Wilson will be asked. Adrian Peterson will be asked. Black coaches will be asked. Everyone's going to have to say something. Even saying nothing will be saying something.

That's what activism is. It is taking on risk to stand for what you believe in. There will be many players who will not appreciate the position Kaepernick put them in, even if they agree with him. Because he forced them off the sidelines. You can't dance between the raindrops forever. Howard Zinn's famous line is that you cannot be neutral on a moving train. The train has always been moving. Now no one can pretend otherwise. Even if they'd like to. What happens next is everything.

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Email me at leitch@sportsonearth.com , follow me @williamfleitch or just shout out your window real loud, I'll hear you. Point is, let's talk.