Radical Islam? What's That?

From Powerline:

Could radical Islam be responsible for recent terrorist attacks inside the U.S.? That question doesn't seem like too much of a poser, but it was too much for Attorney General Eric Holder when he testified before the House Judiciary Committee today. Rep. Lamar Smith tries to get Holder to acknowledge that radical Islam could have played a role in one or more of the recent attacks, but Holder apparently views it as a trick question: