Dear Ujm,
If the therapist cannot control themselves when the patient is vulnerable, then he is not a good therapist. It may help prevent some sins, but it gives a lousy therapist a shot at a career.
And predators would still chase after their pray. There was a shocking story of a man who “specialized” in troubled girls. You may help prevent one form of abuse become less common. But your not cutting to the root of the problem.