This piece presents some lively discussion about terrorist experts, especially "US terrorist experts."

http://www.cnas.org/blogs/abumuqawam...m-experts.html
. First, let us very briefly review the state of the literature in the study of terrorism and coercive violence. Greenwald is correct that "terrorism" has a pejorative connotation in the popular discourse. In the scholarly literature, though, terrorism has always meant something along the lines of "the threat or use of physical coercion, primarily against noncombatants, especially civilians, to create fear in order to achieve various political objectives." (O'Neill, 2005) Greenwald makes it seem as if states are never mentioned as terrorist actors, but there is a lot of literature on the use of coercive violence by states and state terrorism. Off the top of my head, I'm thinking of Schelling (1966); Mitchell, Stohl, Carleton and Lopez (1986); Kalyvas (2006); and Biddle and Friedman (2008). (I'm sure readers of this blog can think of literally dozens more examples. Please do so in the comments section.)

The literature on terrorism and terrorist groups did not spring forth on September 12, 2001. Researchers at my alma mater and elsewhere had been writing about the phenomena of terrorism and groups who use terror tactics for decades. Sometimes these researchers were doing case studies on Islamist or Palestinian groups. Sometimes they were doing case studies on Irish (PIRA) or German (RAF) groups. And sometimes they were comparing and contrasting varied groups. Walter Laqueur originally published this book, for example, in 1977. Bruce Hoffman published this book in 1999. I'm pretty sure those two guys are terrorism experts without the scare quotes.
Rather long article, but worth the read, IMHO.