Marseille is an interesting mixture and this exerpt from a Wikipedia is probably reasonably close to reality in terms of figures. It explains why there probably isn't as much trouble there:
"Approximately 25 per cent of Marseille’s population is of North African origin, mostly Algerian, and Tunisian. Demographers estimate that in the future, Marseille will be the first city in Europe with an population that is a Muslim majority. The Jewish community is also the third largest in Europe."

Though there are racial tensions, I suppose they have enough on their hands with the transport strike.

I was thinking about the reality of some cities in France and you'd often notice that immigrants who came from other European areas and establish themselves, would at first be wary of the Northern African immigrants and resent their presence. Then, in the eighties and nineties in places like Marseille, you'd begin to see intermarriages. This happened in a family close to us. Their son married a woman from Northern Africa, got disowned and then the grandchildren came and they gave up on the boycott!
Actually I remember social discrimination in some circles in France. THere was a distinct classism in France when I first lived there and it's rapidly disappearing. Even children of privileged 'Vieille France' families are not guaranteed a job as they might have been many years ago.

Chirac has been speaking about the richness of the culture and how all the people are children of the Republic.
He has however resisted any 'quota' system of redressing errors of the past and privileging anyone for jobs.