Protesting is one thing, riots another. The moment that lives, property or anything else of that nature (Grundrechte) are infringed, that is the moment that protesters have gone to far. Protests have the function of giving their thought and opinions voice, so that the government, or their boss (union protests), get a notice of these thought, so that they should include these, as best as possible, into their current workings. The idea is not to harass the state and other uninvolved citizen. Being a protester does not give one the right to attack, damage or commit any kind of crime. Sadly people seem to loose the ability to recognize how far they may go in protesting...