Whether or not he strictly practiced his demon-worship is beside the point. The hijackers drank alcohol and visited strip clubs in the months preceding their crimes. Acquaintances of the hijackers said stuff "hmmm . . . so-and-so never seemed to be particularly devout".
Gad, I suppose if one of the Columbine kids had come from a Muslim family, you would be telling me there was an Al-Queda connection.