Throughout the film it seems as if writer David Foyer and director Zack Snyder are going to reinforce this theme: several times in the course of the film (presumably due to the upbringing of his adoptive earth parent's the Kents) he is seen finding a way to save lives. Indeed, this has been a major refrain of most reviewers that I've heard that it is this stubborn refusal to end a life that marks Superman as an iconic comic book hero.
Some have postulated that The Man of Steel is the first of a trilogy that explores the development of Clark Kent/Kal-El into Superman. This is plausible in that they do not call him Superman in this film. Perhaps he has to earn it. It may be that he has to learn the awful consequences of taking a life for himself.
I would not be surprised to see a third option at work here. Much has been made over the years of the comparisons that can be made between Superman and Jesus: they both came to earth as a baby and grew up to be truly good men, sacrificially giving of themselves for the greater good of mankind. This similarity was even shown in the film itself, between many of the lines of Superman's Kryptonian father Jor-El and John Kent (his adoptive earth father)3, as well as several visual elements Snyder chose to put on screen. In addition, the studios even courted pastors to incorporate clips from the movie in sermons, including someone to put together a resource pack for pastors full of Bible studies and sermon outlines that highlighted the similarities.
But at the end of the day, I have to wonder if the third act climax that caused so much discussion among Superman and comic book fans is due to the fact that Goyer, and Snyder4 just can't bring themselves to believe in an all-good, all-powerful hero. It is theodicy writ in four colors and projected on a screen. In this film, it appears that the producers believe that their hero must be able to fully enter into our human condition in order to truly be one of us. This flies in the face of the Christian understanding that sin us not natural to humanity, that mankind was created in the image of God, and that by willfully turning away and rejecting that image within them, evil, pain and death entered the world. A messiah who is like us in this way cannot save us.
This is where the "Superman as a picture of Christ" metaphor breaks down. Jesus, in the words of the writer of the letter to the Hebrews "...understands every weakness of ours, because he was tempted in every way that we are. But he did not sin!" (4:15 CEV). On other words, Jesus fully entered into the human experience. The earliest Christian credal statements affirm the truth that Jesus was in every way God, and yet in every way man, including experiencing first hand what you and I take for granted.5 The Apostle Peter, one of the ones who would have been an eyewitness to Jesus, writes in his second letter quotes from a passage in Isaiah to describe Jesus, saying that He never sinned nor did He lie. (1 Peter 2:22).
1 Or for that matter, all of the folks in the Metropolis skyscrapers? I myself walked out of the theater thinking that the events portrayed would have absolutely bankrupted the insurance industry.
4 As I was writing this, the fine folks over at Strangers and Aliens pointed me to this story which indicates that Nolan was not at all on board with the plan for the third act climax.
5 See the Nicene Creed and the Chalcedonian Creed