Recently I saw a comment that described how in the present environment in the US, the only interactions a person has with the police are typically of a "negative" context. There are now fewer or no "positive" encounters with police anymore.
It goes along with the decline of neighborhoods. You used to live in an area where the people generally worked in the same industries and rode the same mass transit to get there and back, shopped in the same neighborhood stores, and had one or two police officers patrolling the neighborhood who'd been on that beat for years, and everyone knew each other. Now, when everyone gets in their cars and drives off in different directions to go to work, shop in supermarkets scattered all over, and the police officers drive by in cars, nobody interacts with each other on a regular basis, so there's no 'neighborhood' for the police to be part of even if they didn't just slip through without interacting with anyone. So that's what you get -- you don't interact with the police until something's gone wrong, and that colors everyone's perception of them on top of the current tendency of the police to trot out their military-surplus equipment even when it's not appropriate, because if they don't use it they'll be accused of wasting the money that was spent to buy it.