The best scientific argument against marijuana parallels this logic. We have good anti-emetics and adequate appetite stimulants. If there is pain, surely we can relieve it. Doctors should do what every citizen can do. Join a lawsuit.
Civil disobedience is one way.
Dancing around the government's action to help patients is another. For example, physicians cannot recommend or prescribe marijuana. Physicians can discuss its effects, what they know about it, and how it compares with other substances, including legal ones. But not recommend it. For many physicians, the question comes down to whether or not marijuana works.