The AMA should stop pretending that its major concern is the welfare of patients and the autonomy of its members. It's better terms for its members. A union is probably just one more roadblock doctors will use to try to stop the runaway Hummer of managed care. The effects Unionization doesn't change the doctor-patient relationship, or the ethical principles that govern it. It could change how, how much, and when doctors are paid for doing what they do.
Unions ensure that individuals are treated fairly.
If gigantic corporations treat professionals badly, and we cannot defend ourselves because of our commitment to our work, then joining a union is the right thing to do. It's just not the main thing to do. Physicians should not form workplace alliances with those who do not share these ethical priorities. Strikes reduce access to care, eliminate or delay necessary care, and interfere with continuity of care. Each of these consequences is contrary to the physician's ethic.