Pope Benedict XVI quoted criticisms of the Mohammed by a 14th Century Byzantine Christian emperor, Manuel II Paleologus in a recent speech in Germany;
“Show me just what Mohammed brought that was new, and there you will find things only evil and inhuman, such as his command to spread by the sword the faith he preached".
For a different approach at dialogue listen (browse down the page) to Robert Thurman.
Related;
Muslim Leaders Assail Pope’s Tough Speech on Islam
Pope hits out at Islam
Google News coverage

Robert Thurman does not seem to want a dialogue with Bush supporters.
I've read the Pope's speech and think the parts about "broadening the concept of reason" are far more important than the parts about Islam and violence. The crux of the matter: