Its mostly a matter of generation, methinks. French people over 65 have grown up in the 40s and 50s with the Iron Curtain, Cold war, nuclear threat and also all the French colonial wars (Vietnam, Algeria) where the pigmented people are somehow menacing and not quite "French".

In their days, there was (mostly) no ethnic diversity in France; the economy was safely within the nation's border where everybody spoke French. 21st century world is a much scary place for this generation and tough guy macho rhetoric has had some success as seen with Sarko's electoral numbers in 2007.

The generation coming behind (that would be mine) is different: ex-colonies were all independent when I grew up, globalization was well underway even in the 70s and you have to be fluent in English to go anywhere (damn useful to communicate with all kind of people too). This generation is much, much less receptive to the traditional (and xenophobic/racist) right wing discourse.