I don't think Islam is much of a threat at all to the U.S. or any other western country. Islam doesn't have much political power in the U.S., so there is no threat of "Sharia Law" as the far right wants you to believe. We only have one Muslim congress member and he is very liberal.
Islamic terrorist attacks make the news multiple times every week, but these attacks involve just a handful of individuals. These attacks feed on the dysfunction of the Muslim world and the sense of humiliation at the hands of the West.
There will never be a global jihad against the West as Osama Bin Laden would like to see and right wing commentators claim there to be. There is more of a civil war within Islam. Most people are aware of the Sunni and Shia divide(Abu Mussab al-Zarqawi, the former head of Al Qaeda sent a letter to Osama Bin Laden in 04 saying that Shiites were more of a danger then the U.S.), but that is just one of many divisions in the Islamic world.
Chechen seperatists in Russia, Pakistani-backed militants in India, Shiite warlords in Lebanon, and Sunni jihadists in Egypt all have their own distinct agenda, friends, and enemies, and they would love to rob each other of their representation of Islam. Each of these jihadist organizatiions are really nothing more then small local gangs of misfits hoping to attract attention through acts of evil.
Criticizing Islam may be popular in the U.S. where we are for the most part isolated as a somewhat island nation, rampant Christianity runs rampant. In the U.S. Sarah Pailin Glen Beck, Bill O'Rielly, (many in the US Senate and House of Representative), the Alabama govornor, and the list of others run rampant.
I think some have a lot of nerve to criticize radical Islam in Europe, and elsewhere while allowing radical christianity to continue at home.
To the original qeustion of the thread, are atheists afraid to criticize Islam? I think just about all non-Muslims are afraid to criticize Islam, and rightfully so. Most Muslims are good people, deluded, but still good people. The problem is that the small percentage that can be called "radical" or "extremists" are willing to commit acts of violence in the name their faith. We only have one life, and noone wants their life cut short by some religious nutjob.
Another reason to why I think many well known atheists don't attack Islam publicly is because they see that the majority of the people that are attacking Islam publicly are whackjob Christians and they decide that they want to attack the whackjob Christians istead by calling them Islamaphobes to make themselves seem like intelligent people tolerant of other peoples beliefs.
Let me clairify this,
All religions are pieces of shit.
criticize Islam? Sure we do! but the the radicals are savage lunatics, so we criticize
from afar ;)