Of course the obligatory First Amendment concession, but to the real issues involved. I can make a logical argument for patriotism, one that isn't purely emotional. Everyone should understand that most of the things they take for granted in life - electricity, trash pick-up, things running on time, etc. - is the product, in some shape or form, of the state at work. It's so abstract that it is often difficult to see, but we experience the state - quite concretely - in each of these things, including every time we flip a light switch or stop at a red light. As such, everyone should pay proper respect. I call this "patriotism," but others can think of more euphemistic terms if they like.
In this particular case, the state - the American state - provides the conditions necessary for the game of NFL football. If this be in question, I ask any of you whether or not a NFL game could occur in a Syria, a Somalia, an Afghanistan, or even a Kenya or Zimbabwe. The answer is, indubitably, no. So, the American state is responsible, in a sense, of providing us with the sport of NFL football and in providing Kaepernick with the environment necessary to earn millions off of athletic talent and sport. In this sense, his decision is disrespectful at best.
But, as far as his perspective is concerned, I find it far too general to take seriously. I think it yet another product of the all-too-quick to react political environment that our news media and venues like social media have enabled. We had best stop this recent era of a false racial reality - current narrative that these are the worst tensions in a long time; current narrative that black people are being gunned down by police left and right; etc. (although we should not avoid the reality that racial injustice does indeed exist) - that is perpetuated by news media and social media, before we end up creating the reality we think we seek to fight.
We don't want to self-fulfilling prophesy ourselves into the reality we currently, falsely, think we're in. Should that ever happen, white people will go tribal - thinking of themselves as "white people" foremost, rather than faceless, default Americans - and the result will not be good. We've already seen hints of such a future with the Trump campaign's appeal, and we've already seen the reality of such a future in the former Yugoslavia, as Burhead pointed out.