You can't ,but you can't live without them either.....not all are bad ,but you have no way of knowing just which ones are....Just one bad apple can start to whole bag rotting....:(
The only purpose of a government is to prevent any other group from taking control. The duty of a citizen is to control his government. That is why governments always eventually treat citizens as enemies of the state. And cops are the soldiers in that war. There are no "good" cops. They are your sworn enemies right from the start.