They certainly wrote Superman into a corner. He didn't seem to have any other option than to kill Zod. I hadn't made the connection to Nephi, but that comparison breaks down for me because their paths to deciding to kill are completely different. I see as more similar to the defense of "freedom, and our peace, our wives, and our children". Under the circumstances, Superman was right to kill Zod. It was a war in defense of his freedom and his people, and the only way to stop Zod was to kill him.
You probably have a point. The Nephi/Laban comparison is a very different case, because Laban is out cold from being drunk.
I think the reference to Moroni's title of Liberty also is helpful because it points to what Supwerman is in: He is fighting a war against Zod.
I have read some places where people say in response to comparisons of other killings "yes, but that other killer was a soldier, killing is allowed in war."
Well, the Superman is clearly at war with Zod.
Of course, because Superman is Superman he is held to a higher standard. But I do not know it quite holds up when we consider that Zod is also a super-powered being.
I do get the impression that the creators intend Superman to resolve on his no-killing rule as a result of having killed Zod. Some people respond "do you have to kill to know not to kill". Well, the problem is that most people will accept killing to stop an active and rampaging killer, which Zod clearly was. To move up a step in moral restrictions, to not killing at all, under any circumstances, either requires Superman to have thought deeply on the issue (which is unlikely, because until Zod showed up, he never dealt with anyone he could not actually subdue, and seems to not have done any crime fighting, as opposed to disaster rescues, at all) or to have someone impose a specific code of "what you cannot do under any circumstances" rules, most likely by Jor-el, but that is not the type of mentor this Jor-el is.
