Not sure what you're talking about, but the NFL has a reputation for giving players multiple chances. There are quite a few players who don't tow the line and get away with it. Ezekiel Elliott got suspended for six games today and the Cowboys will welcome him back with open arms on Week 7. This has nothing to do with race. Do you watch the NFL? Do you know where Kaepernick stacks up against his peers? Kaepernick is a one-dimensional QB that is very easy to scheme against.
He's a QB who can't consistently go through his progression tree, so choking off all of the "quick" routes pretty much shuts him down as a passer. He usually checks down to his RB out of the back field or tucks the ball and runs. Very easy to defend when your average NFL middle linebacker weighs 250 lbs. and runs a 4.6 40-yard dash. If you look at his early success under Harbaugh, the 49ers designed and ran a modified Pistol Offense because Kaepernick wasn't picking up the normal pro-style offense they were running with the original starting QB. Once Harbaugh left and Kaepernick was forced to run a pro-style, his flaws really began to show. Adding in his baggage and lofty contract demands makes it pretty easy to see why NFL GMs didn't want to make the investment in him. He'll still probably play this season, though. At some point, a team will get desperate enough to add him to their roster.