Your anecdote is describing systematic abuse. I certainly don't support that. It happens in the criminal justice system unfortunately; however, the answer is to fix the problem, not to quit enorcing laws.
My point is that I would trust the enforcement of the law if the inherent conflict of interest is resolved. As long as it's there, it gives incentive for abuse. This in turn, makes the public resent policemen (seen as tax collectors) instead of feeling safe when they see one.