I wish Anonymous the best of luck. At best, they can release a few names and cut some heads off the Hydra. They will be replaced by equally corrupted politicians, policemen, journalists, etc. They might even be replaced by people that will refuse to be corrupted, at first, until they are offered the choice of plata o plomo (silver or lead = become corrupted or die).
Most likely, though, they will find out which kidnap victim is being referred-to, torture him until he names names, then follow the chain of names, torturing them and their families, and leave them all hanging from bridges.
Honestly, I can't see how this could possibly be a good move. The best move is to pay the ransom or forget about your friend, instead of getting him tortured to death.