Lewis attacks Islam viously in one of the books in the Chronicles of Narnia called "A Horse and His Boy".
The books are allegorical lessons in how one should live their lives in a christian manner. This includes the fact that Christians should fight against evil in the cause of right.
I am all for that.
I recently met a Muslim who converted to Christianity. He relayed to me the story of a Christian woman who was murdered by Islamic Fascists in Lebanon for sharing her faith.
I am convinced Islam is evil, and does Satan's bidding on this earth.