Candid.
"It is demonstrable that things cannot be otherwise than as they are; for as all things have been created for some end, they must necessarily be created for the best end.”
Nature always creates life for it's best possible end. Life is the ultimate gift but nature cannot guarantee that we will see that end as the best. If we could somehow get into the minds of all those like you describe, I would think that most would likely say that they will take whatever amount of life nature can give them.
I hear what you are saying but nature has no choice in what conditions life starts in. Nature, unlike you or I, cannot feel pity for those we think might want or need it. Many in a hard place do not want or need it.
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Now if God is doing the creating and not nature, then he is definitely unjust in creating a defect in a human intentionally.
Intent is all important when judging for fairness and whether God is a good judge or not.
Regards
DL