In that case, I would cooperate* with him. Don't be afraid to ask questions, especially "Why?" and reasons for his thinking. IME, the medical relationship works best when it's a cooperative effort, with the doctor listening and explaining, and the patient helping the doctor help them.

*I make a distinction between cooperate (a two-way street) and acquiesce (passive compliance). Authority figures frequently/like to use the word cooperate when they really mean acquiesce.

Doc