No, 'they' made it about the flag and our national anthem. Trump didn't start this, a very overpaid football 'player' did.  They get paid ridiculous sums of money to 'play' and while taking a stand is always respectable, doing it by trashing your own country and  with the least amount of 'cost' to themselves, is not worthy of any respect. 
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The whole grievance is centered around so-called police brutality against blacks.  There have been some cases of police killing someone who, on the surface, 'appeared' to not be a threat. But put yourself in their shoes. They are targets. They wear a uniform and are hated by all kinds of criminals from gang members to drug dealers and prostitutes.  This has to run thru their mind every minute of every hour of every day. They are human and not robots, so they 'react' with very human reflexes and emotion.  The biggest victims of violence against blacks, unfortunately,  is by other blacks and not cops.  Who will take a 'knee' for all those victims?