So, just as a point of order, what was the last "racial police slaying" that the NFL players are allegedly protesting ?
I only ask because the most recent one without referencing race, appears to have been Daniel Shaver. A white guy killed by a white cop that was either incompetent, dirty, or both, and then exonerated by the same justice system that is supposedly biased in favor of white people.
Point is, anecdotal evidence that makes a federal case out of a couple incidents because of race and completely ignores other cases, also because of race, is not a reason to "protest" during the national anthem in some ridiculously misguided notion that the protest would somehow serve to initiate a sea-change in the entire justice system in this country. The fact is, the backlash against those protests has probably hurt their "cause" more than helped.
Hell, I'd say go read Malcolm Jenkins WaPo editorial about the topic because he basically comes up with a handful of low level issues he'd like to see addressed, like the cash bail system. He's probably the most informed and eloquent of the protest group at expressing a coherent reason behind the protest, and yet his issues are minor, local, and probably best addressed through his local / state government and at worst some kind of local protest or activist movement. Instead, we have a national protest that a solid percentage of the public perceives as protesting the US, the flag, the anthem, or all of the above.
I mean, these are the same guys that bought into the "hands up, don't shoot" lie about Michael Brown. That kind of thing does far more damage than it helps anything.
Bottom line is, the whole "discussion" of race in this country is a bunch of BS. Your very first sentence is 100% accurate and does not need the NFL protest caveat, because, frankly, it's a symptom of the problem you identified in the first place.