I know nothing about the politics of France. I admit that I do not pay enough attention to it. But, there was an interesting question on a Google Group about whether the cars being burned would be paid for by insurance.
I dont have a French policy handy, and even if I did, I could not read it. But, in the US the cars MIGHT be covered. The question would turn on whether this is an act of war.
My position: its not an act of war (its not even terrorism) and should be covered. Insurance is designed to cover acts that are not expected to occur. You do not expect people to begin burning your car, or the cars on a street or in a city. It seems to me that these cars should be covered.