I have a good friend who was a cop for 5 years.
I have spent alot of time talking with him on many situations, and ones like this too.
I've also personally seen police abuse their authority on several occasions, and also in situations I witnessed that were not directed at me.
No one's perfect, as there are good and bad on both sides of the law.
I'm sure it is hard to deal with people like this day in and day out.
I have always been polite and respectful to the police, and I've only had a few minor traffic tickets in my youth(none in alomost a decade). I was always met with a hateful and disrespectful attitude, no matter how nice I was.
As I said I know not all police are this way, and everyone is entitled to have a bad day. There is however a certain amount of proffessionalism expected.