It would only be a protection racket if the cops were conspiring with those who commit the robberies. Lots of businesses pay for security for all kinds of obvious reasons; just because the cost of security is deemed to be lower than the cost of not having it doesn't mean that anyone is running a "racket".
But the DA and police chief choose not to pursue property crimes or even assaults... the officers themselves are probably not conspiring, but it's a culture of "leave the criminals be" which leads to needing this extra protection, and it's all coming from the same organization.