I couldn't disagree more with your premise. You can't extrapolate a single example and apply it to the whole profession across the world. There are examples of people in every single profession in the world who abuse their position - doctors, teachers, clergy, even lawyers.
Using your premise you couldn't visit a doctor (he has the power to kill you), send your kids to school or church (the teachers or priest could molest them) or divulge any information to a lawyer (who could use it for any nefarious purposes).
The part in bold is the point I have most contention with - in most of the developed world we don't have systemically corrupt police forces any more than we have systemically corrupt or perverted hospitals, schools or churches.
I suggest it is attitudes like that which makes policing a much harder job than it should be, and our society as a whole suffers as a result. Unless you live in a country like Iran then the innocent have no reason to hide or withhold information from the police going about their lawful duty.