The point of autonomy isn't to treat the patient as the most knowledgeable person in the room, but to present the options, all considerations and drawbacks that you're aware of, answer any questions, and then ask them to make a decision. If you think that patients aren't smart enough to understand the implications of drug side effects and weigh the costs and benefits of treatment versus the original disease, then I really hope you're not a doctor. And I really really hope you're not my doctor.