In most places, about 30 to 250 people are rioting, and causing damage, but so many people are ready to attribute their actions to an entire country or religion. Think of it this way: do the Occupy Wall St. protests and rioters in Oakland represent all Americans? Of course not--they represent some Americans, but not all of us, and their actions do not reflect anything about a majority of Americans.
Also, people who keep asking why Muslims, etc., don't counter-protest or condemn certain actions, 1) people have jobs and families to take care of--let's say you opposed any rioters who were part of the Occupy Wall St protests. Did you go to Oakland, etc. and counter-protest? If not, why would you expect anyone else to? 2) Also, let's say you did condemn the Occupy protests or damage in Oakland--so what? Do you think anyone who thinks America is a police state cares what you think, or that your condemnation accomplishes anything effective?
At the end of the day, most people want the same things--to take care of their families and to have a job. Countries with many unmarried, unemployed, or uneducated men are going to have problems regardless of religion, race, or background.
(Edited to add paragraphs.) Via Rafat Channels Tullock, Kuran, and Sunstein, Bryan Caplan | EconLog | Library of Economics and Liberty.