The portion of the novel given in the movie doesn't directly touch on it - you're absolutely right. But the entire thesis of Atlas Shrugged is an indirect attack on the message of the Cross.
The famous speech by John Galt near the end of the book - over 25,000 words and probably over three hours long if it were actually recited - is effectively an extended assault on the notion of the righteous sacrificing themselves for the good of sinners.
While the sequel will likely never be financed and while the producers would probably never inflict the full text of that wooden speech on an audience, they would not be true to the novel if they did not drive that point home - since that is the core thesis of the book and of Ayn Rand's whole notion of "the virtue of selfishness."
I was about 30 when I read it, (and the Virtue of Selfishness) and remember thinking about the “selfishness” of her stances...even though I wasn’t particularly religious at the time and kind of in my own little selfish world. And, I hated that long “speech.” I probably should go and re-read other parts of the book, though, since it’s been quite awhile. On the other hand....I think we’ll just go see the movie.
Not even a Judeo-Christian ethic advocates a mindless altruism or self sacrifice. The Cross is not God saying “let’s give it our best shot and hope some sinners out there get the hint” — but a promise. The giving itself is intended to be a picture of God’s purposeful sacrifice. A wise one does not keep on shoveling pearls at pigs, to use another biblical maxim.