[Alberta's Child]

Your argument seems to be that the two things are dissimilar because flipping the bird is always misconduct, while kneeling is only misconduct in one set of circumstances.

Well, yes. The two things are dissimilar because one of them is almost certain to be considered "misconduct" in a legal proceeding -- while the other one is not likely to meet any objective definition of "misconduct."

This is why written rules are so critical in any labor dispute. Labor law does not look kindly on any type of disciplinary measures that can be construed as being arbitrary in nature. Without documented rules in place, a player who kneels during the national anthem is likely to be considered no less respectful than one who closes his eyes or looks down at the ground.

[dsc]

“while the other one is not likely to meet any objective definition of “misconduct.”

I think a good lawyer could convince a fair jury that it was, based on the players’ own statements regarding their motives.