Here is my previous post on terrorism and the likely future suspects. In my humble opinion, American Muslims do not generally represent a serious threat to any state's security. Every group, however, has radicals, and we ought to focus on the methods governments should use to monitor perceived radicals. In short, balancing civil liberties with security is the real debate.
May God bless all the victims of 9/11, including their surviving families, and post-9/11 hate crime victims.