The complications are that
a. this "therapy" is often performed by para-professionals (religious leaders who have no or little training in therapy, etc)
b. the "informed consent" argument is illogical--if an anorexic girl came to you asking you to help her get down to 70 lbs, would you give a little informed consent speech and do it? Of course not--you'd recognize that social influences are negatively impacting her personal goals, and work to fix the goals not help her meet them
c. the therapies are demonstrated to not only do nothing, but to harm. Sue Morrow's longitudinal work on the topic has lost participants who kill themselves during the "therapy," including those who never attempted suicide prior to the therapy.