It's an interesting problem imo. We don't know for certain that, for example, chemo will work, so we have a kind of faith, say a faith in scientific probability. Others have a faith in some other force, and if the child survives then their view is vindicated, though not from the scientific perspective. The starting point for some in this discussion is that life is greater than death. Others put life and death on equal footing, indeed, as two sides of the same coin.The problem is that the child is being left out of all this. If he's mature enough to decide for himself, like that teen girl who wanted to opt out of chemo, that's one thing. But we're expected to care for children, not sacrifice them on the altar of our own beliefs.
(Smiling at Tsing's last paragraph re "weird".)