I wrote before on France, and the marginalization of minorities causing alienation and ethnic strife. That was triggered by police chasing an immigrant youth who hid in an electric station and died when shocked by the current. Days of rage followed with confrontation between police and immigrant youth. Lots of property damage ensued.
Now, the same is happening in Greece riots (also, BBC news, eyewitness account, and fresh riots).The police shot a teenager dead and the streets erupted with violence, confrontation, damage and looting. This spread to many cities across the country.
There are of course differences, but I believe that the similarities are what matters here. There are no immigrants this time. No different skin color, nor language, nor religion. Both the police and the rioters are ethnic Greeks, speak Greek, and belong -- largely -- to the same church.
The riots have been happening for some time to oppose government corruption, crime and police inaction. Yet, the trigger event, death of a youth at the hands of the police, is very similar. It inflamed people and probably radicalized more. Very similar to events when Benno Ohnesorg was shot in German and lead to the formation of the Red Army Faction (Baader-Meinhof).
The anger also takes the same form: destruction of property belonging to people who are not part of the grievances. Some reports say it was directed to clothing shops and banks in Greece (representing excess and weath?)
In the case of Greece, the polarization is mainly leftist radicalist/anarchist groups (ideological) and the young protestors (generational gap) on one side and the police (power of the government) on the other.
Riots and mobs are one of the most dangerous things. The veneer of civilization, when peeled, reveal raw emotions and destructive forces, regardless of the superficial differences in the causes.