From reading the speech the Pope was specifically making the point that Islam exalts irrationality in contrast to Christianity.
From the speech:
"The decisive statement in this argument against violent conversion is this: not to act in accordance with reason is contrary to God's nature. The editor, Theodore Khoury, observes: "For the emperor, as a Byzantine shaped by Greek philosophy, this statement is self-evident. But for Muslim teaching, God is absolutely transcendent. His will is not bound up with any of our categories, even that of rationality." Here Khoury quotes a work of the noted French Islamist R. Arnaldez, who points out that Ibn Hazn went so far as to state that God is not bound even by his own word, and that nothing would oblige him to reveal the truth to us. Were it God's will, we would even have to practice idolatry.
http://www.freerepublic.com/focus/f-news/1702938/posts
Nor is the islamic allah bound up in truth or righteousness. He is a lying @sshole and so are his followers.