Have you seen anything (aside from blatantly biased accounts) that proves it is true? Has anyone been convicted yet? If so, I'd love you to share it with the class. I couldn't be much farther away now, so maybe I'm missing something important.
The vast majority of times, when people claim the police are using excessive force, it's in response to lawbreaking and violence from the protesters. Protesting does NOT give you immunity from the law. We are lucky in this country, because we have freedom of speech. However, that doesn't mean you are free to block major roads. If you want to protest peacefully and legally, do so. But that isn't what's been going on here.
But when people break the law, and then resist arrest (when they deserve to be arrested), you can expect violence to break out. That violence isn't the fault of the police, who are doing their jobs and enforcing the law. It's the fault of the people who assume the law doesn't apply to them, simply because they're in a mob.