I think you're missing the point. Colin Kapernick is protesting a country that allows him the opportunity to make millions of dollars playing a game. Kind of like a supermodel who gets paid millions protesting because she has to work too hard. It's okay for a white guy to protest racial inequalities but don't do it while playing golf at a whites only country club. What's next, is Bill Gates going to protest because minimum wage is too low?
We really don't know what he is protesting because he chose a pretty crappy vehicle to do his protesting. As you say, he has a voice so he ought to use it. Empty gestures to try and get back to relevancy is not very worthwhile.