Dear Mr Fisher,
Sex therapy is most certainly a legitimate field. For a detailed explanation, please go to the attached link for the American Association of Sexuality Educators Counselors & Therapists.
If it is sex surrogacy you are thinking of, that is not psychotherapy per se and it is not considered a branch thereof. Sex surrogates are used by psychotherapists as assistants, performing specific exercises with clients referred by psychotherapists as part of a treatment plan. For a detailed description of said profession, go to IPSA's (The INTERNATIONAL PROFESSIONAL SURROGATES ASSOCIATION)website at http://members.aol.com/ipsa1/home.html. People have all sorts of fantasies about sex surrogates, however, the reality is not particularly prurient or even erotic. Many therapy clients who are prescribed sessions with sex surrogates have serious emotional problems which prevent them from engaging in sex acts at all. Also, sex surrogates are not generally "babes," but kind, average-looking professionals who take their jobs very seriously. Of course, the field is not without controversy, in fact your question regarding the legitimacy of sex therapy bears witness to an enduring ambivalence about the entire subject.
As to what happens with objectivity when the client is having sex with the [sexual?] therapist? You can well imagine that ANY objectivity flies out the window, particularly on the part of the therapist. It is unethical, illegal and extremely damaging to the client in the long run, because the therapeutic trust and boundaries have been broken. It is also quite natural for a vulnerable client to develop an attraction toward the therapist. In psychoanalytic terms, we call it an erotic transference. Such feelings are best dealt with openly and frankly in the therapy room and worked through so that the client can progress in the therapeutic process.
The Board of Behavioral Sciences and the Board of Psychology in each state look very seriously upon sexual relations with therapy clients. I get some professional magazines sent to me every month and there are listings of "disciplinary actions" taken against psychotherapists. It's really amazing that despite clear directives, so many therapists get caught having sex with their clients. Mostly male therapists with female clients, but some lesbian therapists with females as well!?! And you know why they get caught? Because 9 times out of 10, the CLIENT can't handle it, spills the beans to someone near and dear, and then gets encouraged to report. The therapist gets hauled in before his/her respective board and depending on the severity of the matter, the professional in question either gets his/her license revoked, or, the revocation is "stayed," meaning probation. They also have to pay back all the therapy fees and various other restitution costs. And yes, there can be ensuing criminal lawsuits as well.
I also want to make it clear that ANY kind of dual relationship is unethical and grounds for loss of license. This means that the therapist should not have any other type of relationship beyond the therapeutic one with the client. For instance, a recent client offered me his ski condo in lieu of payment for therapy sessions. Had I accepted, I would have been guilty of dual relations. Of course there are many other rules and laws concerning confidentiality, disclosure, etc. but that's a topic for another question. Suffice it to say that if you or anyone you know is having sex with their therapist, please report the therapist. It's not fair to abuse the client's trust, feelings or money in such an egregious manner...even the client thinks it feels good for the moment. As I said previously, it usually ends badly and both the clinician and client lose out in the end.
Keep it to the lovely TER ladies, folks,
the Love Goddess
the Love Goddess