Well you can't deny that anarchism has made a pretty bad name for itself with the Dogma of Violence from the past century. Of course, the movement is evolving but the past has a powerful presence.
Also, the fact that anarchists generally would like to reserve the power to hurt other people to themselves and would not give it up to some controlling structure sounds quite dangerous ("I don't care about the laws of the land, the decision what is good or bad lies entirely with me and I reserve the right to use violence to defend my values")
Not that I completely denounce the ideas, but I'm generally careful in declaring support for them.
That said, I think in the next say 10 years, terrorists would still remain mostly Muslim in the eye of the mainstream media. With the small addition of far-right crackpots like Breivik.