As others have said police jobs usually attract bullies since it gives them a sense of superiority and control. It isn't too hard to get these jobs and they don't have that many requirements so its easier for idiots like this to get to a good position. Not only that but most of the time, what the officers do doesn't really have that many repercussions as you saw. They aren't untouchable but they are pretty difficult to punish.  Edit I should also say not all officers are like this. Most of them are actually really fucking cool. The prick in the video and the assholes in the news are fairly rare.