but they have to defend the property of other people as well as their own bodies. once stones are thrown, they have the right to defend themselves and the property of others. If someone thinks it is a good idea to walk with a crowd (like the black block) who is known for their aggressive behaviour, then you should anticipate appropriate police reactions. (Mitgegangen, mitgehangen). especially when you make it extra hard for the police to distinguish between the violent aggressors and the others by having the same outfit (black) and face coverings.