I know Canada and the US are a little different, but their policing practices are largely founded on the same principles. This makes me think of when I was a teenager, knew everything, including my rights. Stopped with a group of friends on foot for the simple offence of looking like trouble.
Officer: Can I see some ID?
Me: Why, am I under arrest?
Officer: Do you want to be?
Me: Here's my ID.
Officer: Thank you. Let's not see any trouble out of you guys tonight, OK?
Me: OK.
At the time, I was pretty miffed. I knew that, even though I had done nothing, it would not be hard for the officer to conjure up grounds for arrest. However, looking at the situation with 15 years of life under my belt I understand the usefulness of this type of policing. Let most people away with minor technicalities, and then when you know something smells, you have several lawful excuses at hand which you can use to initiate contact.
This does not excuse an officer from over-reacting. In policing especially, professional conduct is critical. That being said, lots of police officers work on the edge, and can easily be pushed in to some sort of misconduct. Imagine going to work and having to deal with other people's problems, all the time. Almost everyone you talk to does not want to be talking to you. You shovel other people's $hit all day. It's easy to slip up.
Most police officers I know will readily point out that most people who get in trouble talk themselves in to it. Some officers operate differetly, but most I know go in to a situation willing to give a break, and it is your conduct that determines if that break will stand. Of course, this relates to minor offences only. I don't know any police officers who will look the other way at a serious crime because you remembered you manners. In effect, though, this is their way of finding out who is behaving, and who is trouble. If you get stopped for a minor offence, and you cop attitude, or try to run, the officer has a pretty good idea what you're about. If you act like a grownup, they'll often give a token warning or fine and move on to the troublemakers.
There seems to be a lot of police conversation on motorcycle forums (go figure). At the end of the day, it's important to remember that police officers are people. Some of them are great at their jobs, lots of them are good enough at their jobs, and some of them just plain suck at it, just like any other job. Sometimes you'll end up talking to a jerk, but for the most part, police officers just want to get through the day without a major incident, just like you do at your job. If you can show them that you're not likely to be the root of a major incident, and treat them as you would like to be treated, you usually won't have a problem.
On the days when you do get the jerk, they have more privelleges in society, unfortunately for you. That means they can do things that interfere with your freedom. This is an unfortunate by-product of policing. If we can't trust police with these privelleges, though, they become ineffecteve. At the end of the day, even the worst cop you have ever met would probably pull you and your kids from a burning car and administer CPR until the ambulance arrives. Heavy stuff. As much as it's hard at the time, remember what a police officer deals with in a day before you criticize them for being short.
This dude got his rights stepped on, and that's not right at all. He could have helped himself, however, and he didn't. Everyone loses.