OK here's my idea:
Put him in prison. Brainwash him so that he becomes either a devout Christian or an atheist. Get him to make another video from his cell of him totally denouncing Islam and terror tactics, and calling Mohammed a heathen or something, and broadcast it from al-Jazeera or some-such.
What good's that going to do (apart from the fact that it's near impossible to "brainwash" somebody).
Everybody seeing it will recognize it was made by torture. It would just lower everybody's esteem for the US, and make Islamists madder than ever.