Why are they calling the disturbances riots?
Simply because in law that is what they are:
Riot is now defined by s.1 Public Order Act 1986, as follows:
(1) Where twelve or more persons who are present together use or threaten unlawful violence for a common purpose and the conduct of them (taken together) is such as would cause a person of reasonable firmness present at the scene to fear for his personal safety, each of the persons using unlawful violence for the common purpose is guilty of riot
