of course that's the simplistic overall view, the intention is to create a divide, they won't get backing for their strict Islamic ideologies from Muslims who have integrated and embraced western culture .
The terrorist attacks have created a divide in many ways, yes, too many, and in these ways the terrorist attacks have done what they set out to do. The fear is there and many westerners now, very wrongly, treat all Arabic looking folk with an air of suspicion. I personally don't feel that any Muslim I encounter needs to speak out against these actions before I trust them, I will treat them as I would treat anyone I didn't know, I'd assume they were anti-terrorism until they suggested otherwise because it's not natural of anyone to support such horrendous acts, regardless of faith / race.
You say if one could tell the difference between moderate and extremist Muslims, then that would go a long way towards outlawing the radicals from our society. If one could spot a murder, or a rapist or a paedophile we could get them too, we, unfortunately, can't!