I also agree we shouldn't jump to conclusions, everyone thought Norway and OK City were Islamists and they were wrong.
I was living in the US at the time of the Oklahoma City bombing. It wasn't so much that the TV reporters etc 'thought' it was carried out by Islamists (I don't think the term had been invented then, anyway), more that they couldn't believe that it could be home-grown all-American terrorism.
As for the nutters on this thread blaming Mossad and 'the zionist press': guys, I cannot take you seriously. I do, however, take men in black with AK47s horribly seriously, because they want to change, forever, the way we live our lives, and they will do it by force if we let them. They are bloody terrifying. I do not want my daughters and their daughters forced to wear hijabs 40 or 50 years down the line. I don't want them to have to live under Sharia law.
So what do we do? Blame the Jews/Mossad/Zionists? Well, that will really help, won't it? Or get heavy? Or work with moderate Muslims? I hope we try the last option, and I hope it works. If it doesn't, well, we'll look back on threads like this and the dream-days of freedom as paradise, I suppose.
Being scared is not giving in. Being scared seems entirely reasonable to me. Hanging onto the freedoms of liberal democracy and toleration seems the only logical thing to do.