A key sentence from that article by Frank Foley in the BBC News Mafazine:

"A fundamental underpinning of the post-9/11 interrogations was a belief among security officials that their brutal treatment of detainees would remain largely secret."

And that is why openness is so important at this stage. "Everyone already knows about it, so why drag it up now" misses the point. The perpetrators at all levels are still protected, the lower level ones by continuing secrecy, the higher up ones by the untouchability that clings to those who are seen as important. And in the case of foreign leaders such as Tony Blair and Jack Straw ( among many others), by both secrecy and status.