I don't think there is anything wrong with presenting the patient/client with expertise that they may not have, but the problem arises when the healer (even if it's a medical professional) is sure that they know best, rather than working with the person to find an appropriate intervention. Sometimes, there is no time for that because it's an emergency situation, but lots of the time there is.
At this point in my life I only go to doctors who will listen to me, accept my understanding of my own body, and combine that with their training and experience so that we can come up with a good plan together. I'd like to see a lot more of that, particularly since on more than one occasion a doctor nearly killed my mom with their insistence that they knew best (and she had no muscle for questioning that). It was kind of a miracle that she lived to be 89 because this happened at least three different times (and probably took 10 years off my life). Of course subject matter experts deserve respect, but they also need to respect their patients as well.
Thanks for your thoughtful comment, as always.