I'd be put off if a therapist asked me specifically, "Do you touch yourself?" They can at least ask more politely. Like, do you masturbate, or do you take care of things yourself.. Honestly, if a client were talking about an issue where its important enough to bring up whether or not they masturbate, the client should tell them if they want to, without having to be asked. The client has all the control over what information he or she tells the therapist. And its perfectly fine if he or she decides not to answer the question.