Why the Flag? That's the problem. The flag does not stand for the local police department let alone some other city's police department.
And not all police departments are alike. When that a-hole started shooting at cops in Dallas during a Black Lives Matter demonstration, it was the Cops who saved the lives of folks who got caught in the cross-fire. These football guys are idiots.
Another thing that might be happening is that they might be having "guilt feelings" about making millions while what we used to call in the Sixties "The People" are suffering in poverty.
But if you feel that way, donate some of your millions. That will help with poverty in the ghetto which is one problem. And get involved in supporting and reforming, if necessary, your local police and that will help with reducing crime in the ghetto which is the other big problem.