9/11. Sami Al Arian has been around and operating for many years, and his actions have been no secret to the FBI. He's got very good political connections, most notably to David Bonior via his son Abdullah. The entire left-wing academia/media establishment have been very vocal and very effective in defending him.
Think about him in a similar way to the Sinn Fein, the supposed "political, non-violent" wing of the IRA. He's a front man who raises funds and schmoozes with the pols to give the "fighters" some room to work. Fortunately, 9/11 stripped him of much of his political cover, and gave the FBI the push it needed to shut him down. And it's high time.