That "piece of cloth" is a symbol, a representation of this country along with those who fought for it and it's citizens, not just law enforcement, which is apparently what he's "protesting." As I've asked before, why isn't he "protesting" in front of those police stations, or organizing petitions to send to government representatives to look into these occurrences? Yes, things can get better, I won't argue that, but read his words, he referred to the country and our flag, the same country and it's symbol that's allowed him to pursue his dreams to play professional sports.
And, not that it makes any difference, but it is a fact he's half white, and was raised by white parents who obviously supported him to reach his potential. Simply put, this country, nor our flag discriminated against or "oppressed" that.