The Quran itself is a very violent book, it says to kill any non-Muslims. The only exception are Christians and Jews (people of the book). The Quran says that they should be treated harshly and heavily taxed.
The entire Islamic religion right down to the prophet Muhammad is violent. Muhammad was engaged in war for 10 years straight in his lifetime. He gained his wealth from war, had several wives (including possible pre-pubescent and teenage girls), and he had no problem growing rich in his military exploits. I know there are parts of the Quran which say that violence is bad etc...but they are kind of pointless, because that peace only extends to those that follow their belief system to a t.

BUT, I think that Frances problem is racism, segregation and crappy neighborhoods. You can find similar problems in ghettos in south america. Is that a racial issue?? No of course not, it is a case of people who are dirt poor and have nothing to lose. They engage in illegal activities to try and make quick money and their structure of street gangs becomes so tight that they have the power to fight back against a country like France that has an obvious weak police system.

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"In individuals, insanity is rare; but in groups, parties, nations and epochs, it is the rule." - Nietzsche