If Anonymous has that information, they should be releasing it anyway. What, all the other crimes - kidnapping, murder - aren’t bad enough that Anonymous would want to hurt them, but when they happen to kidnap someone affiliated with their organization, all of the sudden they come forward saying they have all this incriminating evidence? Release the info, these people are criminals.
Also, when or if this person gets released…. they’re not going to be very anonymous anymore. And the FBI will come down fucking HARD on that person. (if they can, since he is clearly in Mexico right now.)