I absolutely agree with each of your examples.  You have very astutely pointed out various ways that people have done something.  As a child of the sixties, I watched MLK march on TV or saw pictures in the paper.  MLK and those who marched with him DID NOT march through the halls of their workplace.   NFL players who really care about systemic racism should do like those who marched in the sixties.  They should move to the streets in a peaceful demonstration, like MLK and his fellow travelers did.  Can you answer the question: "What are the tangible goals of kneeling at an NFL game during the National Anthem?