Ah, dear...this is kinda tough...
Then, if these Mosque leaders are harboring or furthering terrorists, as proscribed by the constitution, obtain the evidence and prosecute.
Look, we had this same crap here in the early 80's. Americans it seems forget WE were the first North American country to be hit by international terrorism. We had bombs going off and two airliners were blown up after bombs were planted on planes here at my very airport. Sikh terrorism was very much a threat, and it claimed several hundred Canadian lives when Air India Flight 182 blew up over the Atlantic killing 329 people. It was the first bombing of a 747 jumbo jet.
Do you think there wasn't some panicked reaction here, where the Sikh population is 20%? We had a Sikh reporter who had threats made on here life as she reported on the reaction of the over all Sikh community. And the word "extremist" took on a broader, less specific meaning; it seemed in some corners wearing a turban was "extremist."
In the end we got the bombers. They will die in prison, we do not kill people here. It may seem too little to some, but what we also got was a more harmonized country, one where white are kinda proud our Sikh brothers tout their turbans and how-the-****-do-they-do-that beards. What we have also is a Sikh community that identifies as Canadian as opposed to "indo-Canadian" who live in peace knowing we won't over-react and put them in concentration camps like the British.
Sometimes democracy sucks. Sometimes bad guys get away with it. Most of the time, though, the innocent don't pay.
I would give some, a bit, of consideration of an ad campaign, different than this, if the US had gone after the spontaneous demonstrator terrorists who killed ambassador Stephens and remain free. That, more than anything else fueled extremism as a whole new generation see that yes, you can attack US soil, kill Americans and get away with it.