protection for cops makes easy prey

It is not difficult for someone to buy a police uniform, or to get a fake badge, then claim he's an undercover cop.    It's illegal, but if that person is intent on harming someone, chances are, they don't really care about those other laws either.  

Police are searching for a man who they said posed as a police officer Sunday evening and demanded cash and sex from a woman in the Lincoln Park neighborhood. 

When you make unequal protection for police officers, you extend that protection to criminals posing as police officers.   I might be thinking of a Utopian society where people can defend themselves from anyone if their liberties are invaded.   Sadly much of police work in the modern day is entirely about invading other people's liberty.  Without special protections, those law abiding citizens might legally defend themselves against such attacks.   The down and dirty of it is that special laws preventing you from defending yourself against a police officer if they attack you are uncalled for, and dangerous.   Police officer should not attack you, and should not make unreasonable demands of you... but they do, because they can, and it's protected.   It becomes harder to tell an unprotected criminal, from a protected criminal every day.