In Islam, it is forbidden to make pictures or sculptures of Mohammad as that would encourage idolatry. This is probably why the artist decided to just cover his face with a turban thing since no one knows what he looks like. Even Muslim religious paintings and movies show him with a scarf over his face. I think that any Muslim will instantly notice this about the sculpture, but not get angry.
I'm more pissed off about the Christ piece as it just looks like a hobo.
There's a long tradition of assassins from the Middle-East- in fact the word "assassin" itself I believe is derived from a society created by noted madman Hassan i Sabbah.
The word "assassin" comes from the word "hashishi" (it's hard to write the arabic pronunciation in English), which means a person who smokes hash....of course.
They were an assassin group that I believe worked for the Syrian king and they would smoke hash for divine power or something, before their missions. They did two missions against Saladin (enemy of the Syrian king). In the first mission, Saladin was laying siege to a Syrian city and they got right into his tent and just left a death threat on his table. The second time, the assassin got caught by Saladin and then he ran away. Still scared the crap out of Saladin.
I heard that the Assassin's Creed game was based on them. Very loosely based on them.