It's a little unclear to me--from the article, I get the impression that it was the wife who released the tape, and that it may have been the wife who taped the session in the first place, possibly without the therapist's knowledge. In that case, does doctor-patient confidentiality apply? Though therapists can request that people don't reveal what other patients say in group/couples sessions and can make future participation contingent on the patients' respect for confidentiality, the therapist can't control what patients divulge.
If the therapist recorded or permitted the recording without his consent, then I would have a big problem with that. When I was in therapy, there was a lot of emphasis placed on getting my consent to have sessions taped, and I believe my therapist also told me up front about what types of situations permitted her to reveal things stuff from our sessions to other parties.
But if the wife took it upon herself to record the session and then chose to release the recording, I don't see what the therapist could have done to prevent that. I think it was a bit underhanded for the wife to take advantage of the supposed confidentiality of a therapy session to obtain the confession, and I question her motives for releasing the tape now, and to TMZ.
