Ask him what kind of Muslim he is. If he is a Shiite, then he is a more radical Muslim, and part of the group that the people who bombed the towers are from. The Shiite make up a very little percentage of the Muslim population, but they are the radicals like Bin Laden and such. Most Muslims tend to be more accepting, but they still all have a grudge with the Jewish people over Israel and the Holy land. It's called Jihad (service to God), which is interpreted as holy war. They believe the Holy land should not be inhabited by the jews. They have been fighting with different people for the holy land. The Crusades in Europe were fought over Israel, and control went back and forth between the Muslims and the Europeans. People like Bin Laden believe that they are performing a jihad by bombing the US because of our culture and its influence on people. They also believe by killing themselves they will become martyrs, or people who died for a religious cause who are usually remembered as heroes. Well anyway, I would just avoid the topic with your friend. When people at my school start talking religion and crap I usually walk away because I am religious, but not nearly as much as the people here who base their life around it.