I agree that this is the best characterization of the issue - it is true that within the story, as depicted in the film, there was no other viable option. However, if you condemn the writers for creating this scenario you are suggesting that there is an objective format to Superman stories such that if it is contradicted, the story then ceases to become a Superman story. What's interesting is that, in terms of plot resolutions, people seem to prefer that Superman can effectively ressurect the dead by flying around the world really fast -so that it spins backwards and turns back time-. That, people can accept, but killing a genocidal maniac just isn't on? Just goes to show that there is very little logic, and a whole lot of personal taste in super-hero film audiences, especially when it comes to Superman. I think the better view is simply to say that the writers took a chance with the way that Superman resolved the film's final problem. Some hated it, some loved it, many were in-between. Writers have taken similar gambles with Superman in the past, also with mixed results. However, whether you liked this particular piece of storytelling or not, at least it is something different from previous film iterations of Superman - which distinguishes it from Superman Returns, which to my mind is orders of magnitude worse than MOS, because it is an homage, done very poorly, to the original Superman film. An imitation that failed to capture any of the charm/wit/excitement or any other quality that made the original great.