The problem with all of the complaints is multifold:
1) The natural tendency of humans to oversensationalize their own memory when stressed. People frequently come up with grander stories than what actually happened, because that's just how they remember it. Doesn't mean it's true. If you deal with enough people on a daily basis then you will realize that this is the way it is. Perhaps you yourself had exaggerated a story or two of your own (i.e. spinning out on the highway in the snow suddenly becomes spun out three times, almost hit by a truck!). Stories are ALWAYS over sensationalized. One prime example is how
Steve Palkin said that his experience at the Novotel was scarier than ethnic cleansing in Bosnia...
2) No one who ever does anything wrong is going to admit it. With few exceptions, people in general are very hesitant to admit fault or mistakes. When actually accused of something, people will try their hardest to make themselves 'innocent'. I doubt many of these people who say that they were just out for a nice stroll to get some milk in the middle of a huge protest that you could hear a mile away are telling the truth. But since there's no way to prove it either way, our system of journalism takes their comments at face value. For instance, notice how the mainstream press always depicts global warming, and then will show off the 'other side' by showing complete wackjobs saying it's all fake but giving them just as much credibility? It's part of our media system of being 'unbiased' that people are taken at face value and not questioned in order to show as many 'viewpoints' as possible. The more sensational the comment (and the less institutional) the better.
3) People in detention giving all of these grevious stories of their 14-17 hours in detention. I liked reading in the paper how some people were comparing it to torture because it was cold and they only had 2 cheese sandwiches. I would like to reserve judgment until the actual people come forward with real evidence. Does 'strip search' mean that they had their underwear on? Does peeing in front of an officer mean, officers were somewhere nearby and not looking? Does being 'fingered' by the police mean a hand brushed by there? You can see how easily things can be misconstrued, overstated and just remembered wrong in a tense situation. So it's really hard to say. I'm going to say for sure, everyone got some kind of cheese sandwich (but maybe only 1) and it was sort of cold in there, maybe 15-20 degrees in the least which was how cold it was outside.
4) Police aren't perfect, and violence is part of their every day job. If you work alongside police enough, you will see them with some pretty bad criminals/drunks/schitzophrenics on a daily basis. People who are unpredictably violent and will only respond to force. Police are used to operating in this environment, which is use a lot of force to get the person they are holding to stand down. Obviously this doesn't work very well in a protest standpoint, but really how many 'professional riot police' are there in Canada, versus regular cops used to using a bit of force to put down a violent drunk every weekend? It's like getting professional hockey players to play a game with normal people and hope that no one gets hurt when they are checked. So what the average person may view was 'police beatings', from their point of view or even from the point of view of another impartial observer, it's the police using physical force to pin down someone they have in their custody. Yes they police are rough, but what are you expecting exactly? You can't deprogram that from them, skills which they NEED to perform their normal jobs effectively and safely.
5) A lot of these protesters were baiting the police. I was out on Saturday and I saw a ton of people swearing at police, shouting at them, staring them down. Basically doing anything they could to get a reaction, which is exactly what they wanted. The police are human too, and while they are trained professionals, under a high stress environment, and especially if they see actual troublemakers (vs normal protesters) mixed in, they will move. People think the police are like those Buckingham palace guards that stand perfectly still no matter what you do or something, but I'm sorry that isn't their job.
6) There's certainly some bad apples out there. Like the general public, the police are not immune to making sexist, racist, and homophobic remarks. That's just life. There's also cops out there who are TOO violent and no doubt some abuses did occur, although more likely on an individual level and not as a matter of policy. In any large group of people, it's extremely hard, even impossible to root out all bad apples or get people to act perfectly all the time. Even the calmest people can get agitated with enough stress, and when you have 20,000 cops, all you need is a few to be stressed and be over the top to tar the image of all the police (much like how the Black Bloc tarnished the image of the mostly peaceful protesters).
Mix in all of these mitigating factors and you are basically guaranteed to get bad stories of police brutality and so on. Does this mean democracy doesn't exist? Certainly not. Does this mean the police force as a whole is horrible? Absolutely not. Does this mean that some mistakes were made, yup.
I for one am just glad that the leaders were protected well, no deaths or serious injuries seemed to have occurred, and that there wasn't any actual wide spread rioting (didn't more stuff get trashed in Montreal when the Habs won a playoff round?).
Suffice to say, all parties will take great pains to avoid even using their name in a sentence 
