A stranger is drowning. You know nothing about the stranger other than that the stranger is drowning. You can press a button, and the stranger will be saved, at no cost to yourself or anybody else. What should you do?
Of course you ought to press the button. That's simply obvious.
But it wouldn't be obvious if at least on average a human life weren't good, weren't worth living. If on average, a human life were bad, were not worth living, you would have to seriously worry about the likely bad future that you would be enabling by saving the stranger. It still might well be right to pull out the stranger, but it wouldn't be obvious. And if on average a human life were neutral, it wouldn't be obvious that it's a duty.
So our judgment that obviously a random stranger should be saved commits us to judging that at least on average a human life is good (or at least will be good).
Now suppose we get exactly one of the following pieces of information:
- The stranger is a member of a downtrodden minority.
- The stranger is currently a hospital patient (and is drowning in the bathtub of the hospital room).
- The stranger's mother did not want him or her to be conceived.
- The stranger is economically in the bottom 10% of society.
Suppose, however, that we get some more specific information, such as that the stranger is suffering horrendous pain that cannot in any way be relieved, or that the stranger will tomorrow be tortured to death. It may still be right to save the stranger, but it is no longer obvious that that's the right thing to do. So the on-average judgments above aren't simply derivative from a general judgment that all human life is worth living or from a deontic judgment that any drowning person who can easily be saved should be saved.
So, not only is the average human life worth living, but the average human life in conditions of significant adversity (being a downtrodden minority member, etc.) is worth living.
Now, I happen to think that every human life is worth living. But in this post I've only argued for a weaker claim.