In sports medicine, we encourage healthy lifestyles, yet at the same time we provide medical coverage for events with predictable rates of injury. Perhaps our attendance at such events even legitimizes the activity. Obviously, some sports are more dangerous than others. This logic goes only so far, however. I think it's useful to draw an analogy with other subpopulations physicians are called on to treat.
Athletes are one such group.
While aware of the complexities, the physician's charge is to provide the best possible care for every patient without judging the ethical underpinnings of the patient's situation or choices. Physicians should be selected on the basis of their desire and ability to provide top-quality healthcare to athletes and for no other reason. In providing this care, we need not endorse the level of risk that some sports entail. This might even require leaving the venue and making public the fact that only lip service is being paid to the quality of care. After all, risks are needed to effect change.