Those circumstances are exactly what is completely wrong about this movie because if it wasn't for them, Superman wouldnt act out of character. The core aspect of the mythology is the love triangle built around 2 people and not some outsider and them.
And the core aspect of Batman is that he won't ever kill. Yet at the end of TDK, he more or less did. But it was generally accepted, but why? Its because it took Batman to a place that he had never been before while sustaining his character. Singer also took Superman and Lois, as we know them, to a place they've never ventured into before. In order to do that you've got to have a solid grasp on the mythology.