One problem officer can destroy an entire department's reputation. Citizens that break the law are called criminals. Police that break the law and their oath are called pigs. Officers should be held accountable just like the general public. If a citizen is accused of a crime, most all US states include that person in their publicly accessible database regardless if they are found guilty or not.
If a person is a thief, then businesses may not want to hire that person. If a cop breaks the law and/or violates a persons rights and is fired, shouldn't the same standard be applied? Chances are that dirty cop will try to find a job in the same line of work.