It is actually kind of sad, coming from Australia, Police are usually seen as a force of good. Granted we do not have as much corruption in this sense as America does but sadly these sorts of positions are built on power and violence (eg non compliance) I think the question you have is if the police stop protecting their own people when they are trying to do their jobs how will they attract new police? as a profession where you will have someone that will be in that sort of job for 10-20 years+ getting sacked does not really mean you will be able to get into another police force (quite the contrary) you will most likely end up in a very low end security position.

This is not really a justification of all the shit they do rather an attempt to explain the insanity.