That is a fact worth noting. My wife and I lived in Montpellier for about half a year and have our own experiences with that particular demographic.
When I was in Marseilles about 8 years ago, I was installing software in a bank downtown. We would work all night and leave for our hotels in the morning. Many times the cars would have equipment stripped from them. We were told by the locals that the Arab population had lots of ties to North Africa. Apparently, there was an auto parts trade. Stolen cars from prior years needed parts. The locals would supply the parts needed in North Africa by stealing parts from cars on the streets. Headlights from expensive cars were frequent targets.
Earlier in the trip, our car was broken into and all of our luggage was stolen. I had to replenish everything at local stores. [Don't let anyone tell you that products are cheaper in Europe. In general, shoes and luggage were the only bargains.] We were told, without proof, that Arab rings were breaking into cars in the area.
Marseilles is also the city with the highest support for the Front Nationale. Every Muslim born in France also gives birth to another Front Nationale voter.