I was just thinking of this again, because I read an article that said Christopher Nolan was against the ending, but David S. Goyer and Zack Snyder wanted it. Snyder explained it by saying that basically, since this is an origin story, Superman doesn't have a code about killing, and how could he get that idea unless he faced a situation where he had to kill someone? Something like that. I kind of see what he's saying.
But it's still questionable reasoning because they could easily have written that into one of the scenes with Jonathan Kent telling him to be careful how he uses his strength because he could kill someone without even trying hard. (Like the scene with the bullies trying to get him to fight, for instance.)
Despite that, I do think if that's how Snyder views it, it is something that he did at least think about seriously and talk about with the rest of the team beforehand. I think, while I still hate him for it, I do expect to see this become an issue worth mentioning in the next film. If it's not mentioned, he's an even bigger idiot than I thought. Thank you for effing up Superman. Go make 'Sucker Punch 2'. No, really, I want to see it.
--sd-7