It is not the NFL or the NFL owners that is ultimately blocking Kaepernick. It is the fans...
Kaepernick is free to protest but he is having to deal with the consequences of a fan lead counter-protest. Some may pretend otherwise but the NFL and owners are fully aware that TV ratings dropped sharply because of the anger of the fans. What owner would hire Kaepernick considering that many fans would cancel their season tickets in protest?
Is he? He's on the team's payroll, suited up, when he's embarrassing them and dishonoring many fans. I cannot figure out why he and his partners in idiocy weren't told to stay in the locker room if they weren't going to respect the flag and the national anthem.
Even that would've been way too kind.