No matter how talented the doctor may be, he needs to ask questions and listen to what your symptoms are before he can give any meaningful help.
The other irony of this is that they do think they have the answer before they hear any information, exactly like the doctor they are warning against. The answer for everyone is to become a JW. In JW teaching, when they go door to door, there is no such thing as a person who doesn't "need the truth", no matter how few symptoms the person has and no matter how happy the person may profess to be. In the parlance of their illustration, the asking of questions is just a charade to formulate a reason why to tell the householder they need the treatment that has already been decided in advance to be best for them