If your eyeballs are missing, I can make an assumption that your vision isn't great just by looking at you. That's not a moral judgement.
Doesn't mean blood tests are useless, and in fact it means we have some idea where to start investigating a potential health problem.
Yes, I agree that there's bias against folks who are overweight, and also that there's a range of risk associated with being overweight. It's pretty clear, however, that obesity is a health concern that we should take seriously. If someone smokes five pack of cigs a day, I'm going to make an assumption about their lung health. There's always outliers that live to 100 smoking and not doing exercise, but it would be a shit doctor if they didn't tell folks not to follow their example.
That's entirely my point though: we can't reason with a deadly virus, but we can with most humans. Or at least some humans. OK maybe a few. The point is, I don't think it's logical to throw in the towel.
That isn't human exceptionalism in my view, either: because I don't believe we're inherently special animals when it comes to how we treat the environment. My point is that most animals inherently exploit resources, and drive others to extinction. We just managed to make guns and power tools and propaganda. Once humans are gone, we have no reason to think that any species that manages to start some technologically advanced civilization will be any better. So either we eradicate all biological life to ensure that it doesn't eradicate biological life...or we try to improve humanity, because despite things, we can often be reasoned with. Humanity has gotten better, even though it hasn't improved enough, when looking at human civilization over the last few thousand years. That's my point: not that we don't deserve calamity, but that we can - if we fight hard enough - try to steer our own species toward a better future for everyone.
Who knows though, maybe if humanity is gone the bonobos will rise up to take our place. They're pretty chill, all things considered.