Bound to happen.. And yes one can say because of GitMo. But I would bet this guy would have gone over on his own if he never saw GitMo. His business would have drawn the taliban to him. But there is more to this story check it out.

Militants found recruits among Guantanamo's wrongly detained By Tom Lasseter, McClatchy Newspapers
Wed Jun 18, 5:24 PM ET

Militants found recruits among Guantanamo's wrongly detained - Yahoo! News

(This is the third installment of McClatchy's Guantanamo: Beyond the Law series, which can be viewed in full at McClatchy Washington Bureau | Homepage)

GARDEZ, Afghanistan - Mohammed Naim Farouq was a thug in the lawless Zormat district of eastern Afghanistan . He ran a kidnapping and extortion racket, and he controlled his turf with a band of gunmen who rode around in trucks with AK-47 rifles.

U.S. troops detained him in 2002, although he had no clear ties to the Taliban or al Qaida. By the time Farouq was released from Guantanamo the next year, however - after more than 12 months of what he described as abuse and humiliation at the hands of American soldiers - he'd made connections to high-level militants.

In fact, he'd become a Taliban leader. When the U.S. Defense Intelligence Agency released a stack of 20 "most wanted" playing cards in 2006 identifying militants in Afghanistan and Pakistan - with Osama bin Laden at the top - Farouq was 16 cards into the deck.