Wow this is a hot potato. I have had some really traumatic (including sexual contact) experience with a past therapist as an adult and several questionable incidents with mental health professionals as a kid. I NOW have a wonderful therapist who has stuck with me through thick and thin trying to undo some of the %#@&#! that was done to me. But it has taken a lifetime to find him. My T thinks it is actually much more common (though horrible) than people think. He mentions that he sees lists of physicians who have lost their licenses due to that kind of abuse in every bulletin of the professional association he is a member of. Even his beloved mentor, which really hurt him.
Keep in mind there are many ways therapists can harm and taking advantage sexually is only one of them. I had a psychologist, for instance, who had me repeat again and again "The reason I think I am a %#@&#! is because I am a %#@&#!." I was 16. Not a reportable abuse but it really affected my life I can tell you even though it seems very minor.
I add again that the therapist I am with now is the best I have ever had. The problem is that if you are extremely unwell,mentally, and you are being abused by a therapist you may not realize it and terrible long-term damage can be done to your soul. Therapists have a position of power and it takes a healthy individual to use that power for overall good not bad. It is not a job for everyone. If my adult child asked for my advice about a therapist or therapy I would encourage them to go for it ... but be aware of how the therapist is dealing with boundaries and the potential for harm mixed in with the healing