Kneeling in protest represents a non-violent form of protest. The American way. Why are you so upset by people excerising their constitutionally protected rights as Americans?
Ingratitude is obnoxious. People whining about being oppressed when they make millions of dollars playing a game once a week for part of the year is not really going to cause me to respect them.
The can do and say as they please. But as long as they act like stupid, self centered, ingrates I'm going to call them on it.
Also, they are completely disingenuous. If they cared at all about the issue they are kneeling over, they would be spending their money in ways that actually promote those causes rather than deliberately trying to piss people off.