#1, I don't worship America. I see many Americans treating the flag as if it were a holy relic and the anthem as if it were a glorious hymn. We are a great nation with tremendous blessings, but we also engage (or have engaged) in great evils, such as ethnic cleansing of our Natives, slavery, abortion, eugenics, pornography, and perpetual warfare. While I love this country and am proud of her achievements, I do not think she is a "shining city on a hill" or a utopia; she is flawed and has saints as well as sinners in her ranks, and she is often in need of reform. There is nothing wrong or unpatriotic about saying that.
#2, Kaepernick is in a position to make such statements. Many look up to him. Unlike many punks I knew in high school who thought they were pretty badass to not stand for the pledge, Kaepernick (because of his position) is doing something that people are actually noticing; he is using his position to promote a dialogue about what he perceives as an injustice. While it's true that many blacks are reaching pinnacles of prestige and power that previous generations could only dream of, there are still millions and millions who live lives of poverty in neighborhoods of violence, drugs, and corruption.
#3, politicians don't care. Just like abortion, drugs, immigration, and war, politicians refuse to solve any of the major problems facing America because to do so would reduce our need for them, which would eliminate their power, careers, and income. They don't want to solve any of the problems.
#4, this is no different than when those on the Right hang up a "Don't Tread on Me" flag or insist that they will fight the government in the streets if they have to in order to protect the country. How is his protest against the system unpatriotic, while the protest of those on the Right are somehow making our Founding Fathers smile from above?
#5, there are injustices in America, especially in the black community. There are. It's one of America's biggest blights. We enslaved them. Then, after we freed them, North and South discriminated against them for 100 years (the North covertly, while the South openly). Then, all the industrial jobs of the cities - jobs that would help blacks - were shipped overseas. Then, the nation cared more about reality television than the fact that black-on-black crime continues to skyrocket, all the while with many cops (not most, but many) abuse their power (against whites and blacks, but disproportionately against blacks). Blacks are disproportionately imprisoned, their sentences are longer, those sentenced to death are disproportionately black, they get sub-par representation in court, their schools are allowed to rot, a majority of blacks are born in single-parent households, and a majority of abortion clinics are put in minority neighborhoods in order to continue the eugenic policies of the founders of the American birth control/abortion industries. America yawns when these things happen, to the point where the only time we'll listen or pay attention is when there are riots in the streets.
I'm not a fan of Kaepernick as a player - never have been - and his insinuation that Castro's Cuba is somehow a haven for equality shows how little he knows about Cuba. But he does know about being black in America, and being a famous African-American doesn't make a person immune to prejudice and injustice. And as a man in a public position, he wants to do some good and make America focus on helping all of us succeed. There's nothing wrong with that. There's nothing unpatriotic about that. He's tired of seeing one major segment of the population continue to languish, generation after generation, and all Americans - especially Christian ones - should share his concern and outrage. Many African-Americans are baptized Christians, members of the Body of Christ, and as St. Paul told us, "If one member suffers, all suffer together; if one member is honored, all rejoice together" (1 Cor 12:26).