Well we could start with my home town. This guy got a slap on the wrist and is still on the force:
http://www.lehighvalleylive.com/phillipsburg/index.ssf/2012/01/phillipsburg_police_detective_5.html
He was later suspected of being intoxicated while on duty:
http://www.lehighvalleylive.com/phillipsburg/index.ssf/2013/09/phillipsburg_police_officer_in.html
But his brother who is a captain on the force investigated and apparently he was not. /sarcasm
But most cops I've been stopped by were thoroughly professional. And they also had me dead to rights. I've only gotten one traffic ticket in fifty years of driving. Even the county cop who gave me the ticket was polite.
There are 700,000 leos across the country. Some of them are going to bad. That hardly makes all of them out of control.