Was he blackballed?
The kneeling started during preseason of 2016. Reid started the first 10 games of '16 then missed the rest of the season due to a torn bicep. But he didn't have a good season according to PFF picking up only a 58 grade, but the Niners already took up his 5th year option.
In '17 Shanahan and Saleh came in. They moved Ward back to FS and Reid to SS. He injured his knee in week 3 which gave Tartt the opportunity to start at SS where he played better than Reid (Tartt 78 grade that season vs Reid 70). But Reid still played 13 games as a Hybrid linebacker / safety. In fact he played 100% of snaps in that role even after Tartt took over at SS.
But then his contract was up. They had Tartt at SS, and they didn't want to pay Reid the money he wanted.
The Panthers signed him in 2018 and he played every game from week 4 onwards.
If he was blackballed it lasted 3 games. But I'm more inclined to think that he was asking for too much money (Reid: "Hey I'm a pro bowl safety" Teams: "Yeah 5 years ago") having got beat out by Tartt and having just spent a season playing outside backer.
And with this in mind (because Reid was never really blackballed) was Kap? Or did he just suck?
In 2015 before his kneeling started he was benched in week 8 for Blaine Gabbert and didn't play another game. He then got beat out by Gabbert again in 2016 camp to be named the starter for Game 1. This is Blaine Gabbert. He got the job back in week 6 because Gabbert was Gabbert but he sucked. He only passed for 203 yards per game and 16 TDs in 11 starts and got pulled from a game for going 1/5 for 4 yards.
Then Shanahan came in and didn't want him for his scheme and other teams simply looked at his form the last 2 seasons where he was beat out by Gabbert twice and decided they had seen enough and that he wasn't starting caliber. It's not like he's the first QB to start a bunch then wash out. Blake Bortles has far better career stats than Kap.
Kap has become this social justice folk hero to the point that it's erased what a garbage QB he was. His BEST career grade was the 2012 season he went to the SB with a 73 grade.
His best season for yards passing was 3369 in 2014 which when combined with 639 on the ground was by far his best year. His only good year really. Blake Bortles had a 4400 passing yard season to go with 310 on the deck.
Kap's season grades for his career according to PFF? 73, 67, 64, 47, 58.
It's convenient for the social justice warriors to say Kap is out of the league because of his politics, it keeps the story going. It's a drum they can beat forever.
This simple fact is that Kap sucked. Really badly. Certainly nowhere near enough to warrant a starting NFL job. He was a considerably worse player than Bortles and Bortles can't get a backup job. More and more teams want a backup with upside, someone that might develop. It's much more common now to see the backup be a Wolford, Streveler, Hundley, Allen than a Stanton or Gabbert (both old school BA guys) who the league already know are has beens.
Hell, Winston and Marriota have FAR better stats and grades than Kap and are only just clinging on in the league.