When you take the context and timing of it, it's obviously supporting his friend, but the day before he did it, the French government were trying to ban this comedian and his group from meeting in public spaces, because of their anti-Semitic views. That in itself is a stupid thing to do by the French.

But as for Anelka's motives, none of us will really know. He's a Muslim, so it's not beyond the realms of plausibility he could dislike Jews, but then again he's a footballer, so it's more likely, that he's just incredibly stupid.