The idea that Colin Kaepernick has been blackballed from the NFL is flat-out stupid. It's the ultimate example of trying to create a victim and a conspiracy that doesn't exist.
Kaepernick is a backup quarterback candidate. He also is polarizing because he took a stand that many people found offensive. NFL owners and general managers will overlook a lot of things _ character issues, criminal activity, etc. _ for a player who can help the team win. Backups, however, better toe the line because they are, for the most part, expendable.
That's the issue for Kaepernick. He's viewed as more trouble than he's worth.
Kaepernick became a lightning rod after he refused to stand for the national anthem, protesting the flag because of racial injustice. His stance was that this country "oppresses black people and people of color," and he can't in good conscience honor the flag or national anthem.
Comparing Kaepernick to prominent players with troubled pasts is silly. Ben Roethlisberger and Ray Lewis had off-field issues that were far more troubling than anything Kaepernick has said or done. The difference is those are star players, and the standard is different for stars.
Art Rooney II needed Roethlisberger in 2010, when he was suspended after an accusation of sexual assault in Georgia. He was a franchise quarterback with two Super Bowl rings, so yes, the Steelers were willing to live with any "distraction" he might bring.
The same can be said about Ray Lewis, who was charged with murder in 2000. He ultimately pleaded guilty to obstruction of justice, but his involvement or knowledge of the crime has never been fully known. Lewis will be in the Hall of Fame (when he is eligible), so there was a different standard for his treatment. The Ravens needed Lewis in order to win, which is the bottom line.
Kaepernick deserves credit for taking a stand _ though, as I wrote earlier, he was extremely misguided. However, there are consequences for taking a stand, especially an unpopular stand. Protesters and social justice advocates understand this and have decided the risks are worth taking. They understand they may lose their job, their standing in the community or some friendships _ but they don't care because they truly believe in what they fight for. Kaepernick took a stand many people found offensive, so he has to be willing to live with the consequences. He also doubled down and made idiotic statements about Fidel Castro while wearing a shirt with the late Cuban dictator on it.
The NFL is a business. It thrives because of TV ratings, advertising and ticket sales. NFL owners are in business to make money and win games. So, they have no interest in a backup player who might irritate half of their fans, jeopardize advertisers and/or cause headaches in the locker room.
Kaepernick's problem isn't the stand he took or his skin color, it's that there isn't an owner or GM who believes he can help win games as a starting quarterback. Kaepernick is better than a lot of backup quarterbacks, but that's completely irrelevant. A backup QB is just that _ a backup _ and won't be called on unless the starter is injured. He's a temporary fix. Nothing more, nothing less. That's why teams were willing to sign less talented _ and less polarizing _ players for a role that isn't all that relevant unless there's an injury.
Kaepernick is only out of the NFL because no team views him as a viable starting quarterback. We can argue all day that he is better than a couple of starting quarterbacks in the league, but he's a very average quarterback, at best. The minute a team needs a starter because its starter is injured, Kaepernick's phone probably will ring.