According to the person who posted this at imgur, this is a protest against same-sex marriage in France. Some priceless expressions in that crowd, except, of course, for that woman in the lower corner, second from right. I think she's kind of enjoying it.
UPDATE: The protest took place in Marseille:
One of the girls in the picture, Julia Pistolesi, described the moment on Twitter as “full of emotion,” and thanked those who had shared the image, adding that “homophobes in Marseille can p*** off!”