1930s police actually did have higher standards for their officers. It was a huge deal in the UK and US at the time. Uncorrupt and just police officers were something that the Brits and Americans were very proud of and liked to brag about to other nations at the time (Germany, Soviets, etc).
I think what is most likely is that Araki, being a foreigner, listened to a bunch of songs from the 1960s, 70s, and 80s where hippies complained about the big meanie cops and the awful no good system (that they were trying to overthrow) and he took it at face value. The type of music he references tend to be from the likes of the Beatles, Rolling Stones, and etc, and they're very anti-liberal progressives. Not a lot of Lynyrd Skynyrd, Ramones, Alice Cooper, Meatloaf, or Iron Maiden appear in his works, and likely not in his playlists either. Araki more than likely just hates the police for political reasons.