The inability to adequately and consistently punish cops for bad behavior is the biggest obstacle.
IDK if you guys remember the cop (Brailsford) in Mesa, AZ who shot the drunken Dad in the hotel hallway*. The cop was fired and found innocent of all charges. If that's not bad enough, the city rehired him for a day or a week or something so that he could medically retire and collect a pension. The reason he was eligible for medical retirement was the same incident for which he got fired. He's claiming PTSD. This is a complete cluster****. Kill a taxpayer. Get away with murder. Go live on a beach in the Philippines for the rest of your life on the taxpayers' dime. This is America.
*quick recap: somebody called the cops because he was playing with a BB gun or a toy gun or something. At gunpoint, he was given odd directions by the officer (he told him to crawl towards him on all fours, etc.) and was too smashed to follow directions and the cop panicked and killed him.