My dad tells of how he keeps getting dismissed from jury duty because he is open and honest about his distrust of police.
The thing to keep in mind, though, is that many who become cops don't understand the system. We had a neighbor, a very kind, good man, who was a cop, but when it became clear to his colleagues that he wasn't willing to enforce evil laws, he stopped succeeding. He managed to make a pretty long career of it before that happened because he was a rural cop, and he mostly just made traffic stops (like, actual ones, not in order to search a car).
I have a friend who wants to be a cop because she THINKS it'll be like studying crime scenes and trying to figure out whodunit, not wearing riot gear and pushing peaceful protesters. She's starting to come around, though that just means she's switched her focus to the FBI, and a whole host of further problems.