I think Kap is a total attention-whore douche and I don't like what he's doing.
But I also think you "everyone must believe what I believe, or else" people are not to be thought well of and anti-what-makes-this-country-great.
Members of the military take an oath to "protect, defend, and uphold" the US Constitution. Are you claiming they're all lying or crossing their fingers when they take that oath? Or does your copy of the Constitution have some extra clause at the end of the first amendment along the lines of "doesn't apply to people I don't think 'respect' authority enough"?
I think one of my high school classmates (who has served overseas and has spent over 20 years in the military) said it well:
I am a Soldier. I will always stand and render proper honors to our nation when the National Anthem is being played.
Having said that, the proper response to San Francisco 49ers Quarterback Colin Kapernick is to ignore him.
Forced patriotism is *not* patriotism. If you have to force someone to show respect, are they really showing respect, or are they just showing compliance? And if the difference between the two doesn't matter to you, then it's you who are being unAmerican, not Mr. Kapernick.