I guess I view things differently, maybe because I am "old school". CK (sorry early morning typing) chose to go against the wishes of his bosses, he got fired, period.
I don't really care why he did it, he is entitled to his opinions as much as all of us, but his boss said stand, he didn't.
How many of you would have lasted in your job after telling your boss, "I know you want me to do this, but nahhhh I'm not going to".
He was talented, no doubt, I played college football but would never have made it in the pros, they are gifted individuals. But did he risk more than the construction worker telling his boss that the job was too far to drive to? The migrant worker who said "I'm not picking today, you sprayed insecticide last night", The IT man who said, "I wrote the code my way, not really the way you wanted boss" (OK I know shit about IT). Granted, he was a higher profile than other workers, but what, really, is the difference?
I'll admit I have not studied every piece of news on this but I would believe he had plenty of opportunity to discuss his desire to kneel with his management before, and after, and he should have known being released was going to be the result, unless his opinion of himself was higher than those in the management.
I've owned my own business most my working life, only 10 - 15 employees but still. I used to tell my people that what I say isn't gospel, but I am the boss. If you disagree, or want to do it a different way, talk to me. But, mine is the ultimate decision since the business is my financial risk, if I say do this, and you do that, it sure as hell better work out better and, even then, their job is at risk.