Apparently an attempt to "turn the other cheek." And I agree, it was gratuitous.
That was my thought, initially.
Now I think it's another poke in the eye to the Muslims. A picture of Muhammed saying he is Charlie? That will surely re-enrage the eternally enraged Muslims. They don't want to be in any way associated with Charlie.
You’re probably right that it was a poke.
OKay!