I wonder how much locale affects these results. In large cities, I can see this happening. In much smaller towns, maybe as well. But I have never had an issue with law enforcement. I have had quite a bit of contact with local police and Sheriff Deputies over ten years while in Rapid City, SD, and was always treated with courtesy and respect. The nature of the contact varied as well. Sometimes I filed the complaint, sometimes I was a witness, and other times it was a more social interaction (crime prevention events).
We saw these sorts of claims decades ago about racial profiling and racial discrimination by law enforcement. I am not saying it doesn't happen; I am certain that it does. But my experience has been that if you treat law enforcement with courtesy and respect, they will tend to respond the same way. Bad behavior tends to attract bad behavior. Just saying.