I'd be very, very concerned about terrorists that act "rehabilitated" but are doing it only to get released. These people are not stupid.
Several rehabilitated terrorists released by the U.S. were captured again in Afghanistan. I know their imprisonment might have driven them to do that, but they still fooled their captors by pretending to be totally peaceful.
But there is definitely a subset of foot soldiers that were coerced or tricked into fighting. The trouble is identifying who is hard core, who just wants to go home and live peacefully.