Exactly, they are given an inch... and then interpret the next mile....
For the record, I respect the police as much as i respect anyone else. If i got robbed, I'd call them, because it's their job to assist me. BUT, I would bet money that some police have taken advantage of an "unknowing-of-their-rights" citizen and cornered that citizen into answering questions or complying with their "please do this" by making them feel intimidated and present the point as "you must do this". I know, because I have seen it multiple times in my life at college parties.