Over the top coppers, how would you change the system?

[Flagg]

As you know, every so often a video or story surfaces about "over excited" policeman getting a little too cowboy for their own good. There's a story about one in the news section now. I remember a month ago posting a story about a copper slugging a woman in the face, though it could be argued he had no choice...

Back at the beginning of Aug, these three coppers did this to an 70 year old OAP driver in England because he failed to stop for them:

http://www.youtube.com/watch?v=va0rBKN1Ya4

Now every story has two sides, but I honestly cannot see any justification for this sort of thing. Are the police within their rights to use such force to stop someone who is breaking the law? This sort of stuff seems to happen all over the Western World now. Why does this happen, are these guys new and young, are they just twats at the end of the day or monumentally stupid as to not think anything they are doing is wrong? Are these guys, like anyone else, simply human and now and again fvck up or are having a bad day?