I suspect the non violent ones are probably just not very violent people and don't take their religion nearly as seriously as the fanatics. They are probably more religious than many westerners, but relatively casual about their religion in their frame of reference.
I think they are reluctant to take their more violent cousins to task because of a number of things: 1. their culture places a large value on 'face,' so the are reluctant to diminish their cousins; 2. fear of retaliation from their more violent cousins; 3. basic sympathy for their goals, if not their methods.
In any case, it can't remain that way. Ultimately, their failure to 'clean their house' forces the west's hand to clean it for them, which raises their ire even more.
It's not a good situation, really.
JWR Columnist off the air after ABC/Disney is intimidated by CAIR