Commenter James Elliott quite correctly observes that there was significant French prejudice toward Muslims throughout much of the twentieth century. Since the rise of multiculturalism beginning in the past quarter-century, however, the idea has basically been to allow subcultures, including those of Islam, to flourish with no effort made to assimilate them into the broader society. That policy, along with the aforementioned economic and law-enforcement situation, has worked to isolate and radicalize France's Muslim population.
The important question is, what to do now. It appears to me that economic and criminal-justice reforms are urgently needed in France, not just for Muslims but for all the French, and that the inculcation of a shared French culture must begin forthwith. These measures may very possibly not suffice to create a decent and encouraging environment for French Muslims, but without them, things will only get increasingly worse.
It also seems obvious that the confluence of policies that brought about the current situation in France is something for the United States and other nations strenuously to avoid.