As a 15-year follower of the sport, I call nonsense.
Kaepernick is not a good QB anymore, most certainly not good enough to start for any of the 32 teams. The consensus among industry insiders is that he is at best a back-up and because of this it isn't worth the media scrutiny and hype he will come with. This is even confirmed by a fellow - black - NFL player; LeSean McCoy.
http://www.theblaze.com/news/2017/0...epernick-and-its-not-because-of-his-protests/
As for the firing of players, that hasn't happened yet and I doubt it will. Aside from the massive cost involved and the complex nature of NFL salary cap management, the NFLPA (Player's Association) will fight any form of unfair dismissal, as they always do. Furthermore, the current CBA expires in 3-years and you can be sure that the NFLPA will come out swinging in terms of what players can and cannot do. The owners will also have to think very carefully about what they do heading in to the CBA as the last thing they would want is a lock-out where the best players refuse to sign and play.
Just to shed some light, many owners showed solidarity with their players, including good 'ol southern boy Jerry Jones (owner of the Dallas Cowboys), who is the most powerful figure in the NFL. It is true, some owners have had a change of heart and will now ask their players to stand because they are also businessmen, and the NFL did indeed experience a ratings drop when all of this started. It is starting to recover but they are not keen to see a repeat. The only players who would be at serious risk of losing their jobs would be 2nd and 3rd string players who could be cut with minimal hits to a team's salary cap (no guaranteed money to pay) but the big players probably get fines at worst if it passes the NFLPA.