Christianity vs. Islam in fiction

Can an author treat Islam the way they treat Christianity in fiction? In "The DaVinci Code," Brown creates a secret societ that is protecting the identity of the last scion and the remains of Mary Magdalene. This would prove, somehow, that Jesus and Mary Magdalene had a sexual relationship, and destroy some fundamentals of Christianity. In "The Testament," van Lustbader's secret society is protecting a manuscript that is the testament of Jesus himself that would indicate that he raises the dead by annointing them with the quintessence and was in turn raised by his disciples using the same alchemical formula. This would prove he wasn't God.

So could you suggest the same kind of scenario regarding Mohammed? Is there so much difference between Christian and Moslem that essentially mocking the icons of either would result in insanely different reactions? With Christians, books get condemned, maybe even banned. Someone speaks out against it in outrage. The author says, "It's fiction," and it all fades away. "Satanic Verses" - obviously a fiction/fantasy story - suggests something fishy about the Ayatollah and suddenly there's a fatwah on Rushdie.

So the question is, can you treat religion equally across the board as a subject for fiction, or are there some religions that are simply so volatile that you risk your life touching them?