Right to peaceful protest?

Some of my flist will have already seen yakalskovich's post about how the protest in Stuttgart went so horribly wrong but for the people who haven't, please follow the link. Be warned, though, There's a photo there that's very disturbing both in the agony it depicts and the implications of how ordinary people protesting peacefully against actions of their elected government can be treated as though they were attacking people and setting fire to the barricades.

This level of violence is completely unacceptable and the people responsible for authorising it need to have that made clear to them.