Pertaining to (2), there's actually a lot of empirical data bout what behavior is predictive of good or bad outcomes. It's not just a subjective opinion. Now,

Pertaining to (2), there's actually a lot of empirical data bout what behavior is predictive of good or bad outcomes. It's not just a subjective opinion. Now, you can argue about what outcomes are good or bad, but that's a different issue. In any event, these things aren't as different from other areas of medicine as you think. For example, you're full of microbes at the moment. Some of them might make you feel a little off sometimes, some of them might make you incapacitated, and sometimes it might depend. The decision to seek care and/or intervene is a subjective decision, based on your subjective appraisal of how you're doing, and a provider's appraisal. Does that mean that infectious disease medicine is subjective? Subjectivity enters into all medicine at some point, via ethical decisions about whether and/or how to intervene. Because ethics involves some level of subjectivity, it's unavoidable.