I didn't say the act was consequence free, I just felt it needed to be pointed out that in some cases even Superman feels lethal force is justified.
The thing that needs to be taken, and people forget, is that Superman was devastated when he (actively) killed. He broke down, yelled and wept. He didn't shrug it off it DID impact him. I think that should be taken into consideration.
This isn't like in Batman Begins where Batman tells Ra's, "I won't kill you but I don't have to save you." and just leaves him to die in a train crash without so much as a second thought (Batman who DOES have a well established code of not killing.) Superman killed and it effected him we SEE that. He doesn't shrug it off and he had little other choice. I mean what COULD be done with Zod if he lived?
Batman killed a man who could've simply been captured and imprisoned. Batman. A man who (in comics) once saved the Joker's life when he was mortally wounded and needed to get to the hospital.
I've no problem with Superman killing in this movie because of how it was handled, it wasn't shrugged off.