How does materialism explain truly gratuitous self-sacrifice?
We feel moved by Vander Woude's sacrifice precisely because it seems selfless — the antithesis of evolutionary self-interestedness.
But why is that? What is it about the story of a man who willingly embraces a revolting, horrifying death in order to save his son that moves us to tears? Why does it seem somehow, like a beautiful painting or piece of music, a fleeting glimpse of perfection in an imperfect world?
I'd say that only theism offers an adequate explanation — and that Christianity might do the best job of all.
Christianity teaches that the creator of the universe became incarnate as a human being, taught humanity (through carefully constructed lessons and examples of his own behavior) how to become like God, and then allowed himself to be unjustly tried, convicted, punished, and killed in the most painful and humiliating manner possible — all as an act of gratuitous love for the very people who did the deed.
Why does Vander Woude's act of sacrifice move us? Maybe because in freely dying for his son, he gives us a fleeting glimpse of the love that moves the sun and the other stars.
Which is to say, he gives us a fleeting glimpse of God.
That might sound outlandish to atheists. But for my money, it comes closer to the truth, and does more to explain the otherwise irreducibly mysterious experience of noble sacrifice than any competing account.