They were torturing for actionable evidence. They had people complaining of "spells" and "curses" being placed on them. They needed to find out who was doing these horrible things. They tortured innocent people until they confessed to being the ones responsible.
Now you have people complaining about terrorists. You need to find out where these terrorists are. You torture innocent people until they confess that they are terrorists, and tell you where their secret base is. How many people in Gitmo are innocent? How many have been released after spending a year or more there?