Moral of this story: It is incredibly difficult to determine if a Muslim is peaceful, and yes, many millions are, or if he is a jihad supporter, or even a potential terrorist himself.
What to do? Not sure, but what we're currently doing doesn't seem to be working very well. One key thing we should do is admit the reality of the situation. That would be a good beginning.
Read about one such Muslim who deceived the CIA and destroyed six families in the process of doing so, via Jihad Watch:
Islamic suicide bomber who killed six CIA officers was trusted CIA informant
"As I have pointed out many, many times, there is no reliable way to distinguish a peaceful Muslim from a potentially violent jihadist. It isn't as if there is one sect of Islam that has renounced and rejected violent jihad and Islamic supremacism, and another that upholds such things. If that were the case, one could rely on the peaceful group and shun the group that taught violence. But contrary to popular belief, every mainstream Islamic sect and school of Islamic law teaches the necessity to subjugate unbelievers, by force if necessary, under the hegemony of Islamic law. The U.S. government, of course, denies this fact and bases numerous policies upon the assumption that the vast majority of Muslims share universally accepted notions of human rights, and abhor jihad terrorism. This is the fruit of that false assumption.
'Exclusive: CIA Attacker Driven in From Pakistan: Suicide Bomber Was a Regular CIA Informant, Had Been to Chapman Base Multiple Times,' by Aleem Agha and Nick Schifrin for ABC News, January 2 (thanks to Benedict):
'The suicide bomber who killed at least six Central Intelligence Agency officers in a base along the Afghan-Pakistan border on Wednesday was a regular CIA informant who had visited the same base multiple times in the past, according to someone close to the base's security director.
The informant was a Pakistani and a member of the Wazir tribe from the Pakistani tribal area North Waziristan, according to the same source. The base security director, an Afghan named Arghawan, would pick up the informant at the Ghulam Khan border crossing and drive him about two hours into Forward Operating Base Chapman, from where the CIA operates.
Because he was with Arghawan, the informant was not searched, the source says. Arghawan also died in the attack
The story seems to corroborate a claim by the Taliban on the Pakistani side of the border that they had turned a CIA asset into a double agent and sent him to kill the officers in the base, located in the eastern Afghan province of Khost....'"