The letter is online at the website of the magazine Islamica.
At the Islamica website is also a piece by John L. Esposito that discusses the Pope's lecture and the Muslim reaction.
Have Muslims over-reacted to the Pope's statement? Their responses need to be understood in the context of our post 9/11 world with its greater polarisation and alarming increases in Islamophobia. Many Muslims feel under siege. A Gallup World Poll of some 800 million Muslims from Morocco to Indonesia indicates widespread resentment over what respondents see as the denigration of Islam, Arabs and Muslims in the West. The cartoon controversy in Europe demonstrated both the dangers of xenophobia and Islamophobia, and the depths of anger and outrage. Therefore, it is easy to understand why Muslims would express their disappointment and anger and call for an apology and dialogue much the same as Jewish leaders strongly urged meetings with the Pope or other Church leaders for offensive comments or actions. This was the case for American Jewish leaders before the papal visit of 1987, after Pope John Paul II had met with Kurt Waldheim. As prominent Muslim leaders noted during the European cartoon controversy and in the current situation, expressions of concern or outrage do not preclude discussion and dialogue and certainly never justify acts of violence.
Yeah, it's easy to understand that people are justified in chopping off the head of a priest who wasn't even Catholic because they feel they're being denigrated by an old man who lives on another continent. Got it.