Translation:Please don't call the police!
The police are not very reliable in Mainland China, and Chinese people are not always eager to call the police even when they have been the victims of a crime.
My understanding is that the police are not terribly effective, but I don't believe that people are generally afraid to call the police.
This might sound odd, but I always looked forward to registering with my local police in China. They always seemed so friendly. But yes, friendliness and effectiveness might not always go hand-in-hand...