I am not a T, but I am a medical professional. I can tell you this, every medical professional has to take classes on ethics. I don't recall specifically being told not to have sex with clients but the bedrock of medical ethics is Nonmaleficence: “First, do no harm” Do not have sex with the client is as obvious to any professional and as unnecessary to specifically say as it would be to state do not punch the client in the face. No one is going to list every single possible variation of what could be considered harm, it is left to the judgement of the professional as a professional but also as a human being. What he did to you was wrong on both counts.