That might have been funnier if Batman hadn't killed people in his films too.
I remember in the Justice League cartoon series, there was one episode that explored Superman killing Lex Luthor in a parallel universe, and it let to the JLA putting the entire planet under totalitarian rule.
Personally I have no issue with MoS when it comes to the killing of Zod.
Superman was shown basically being able to hold on against 2 powerful adversaries barely by the skin of his teeth.
He gets one
opportunity to stop him for good, which he might never get again. I think he had no choice but to take it.
I can see how Superman purists would be butthurt by the way it was written. I suppose the story could have provided another way. The whole point was that this wasn't supposed to be our father's Superman.
Sadly it failed miserably in other areas, but the treatment of Zod was fine. Even the original movie was edited to imply Supes threw Zod down the ice cavern to his death, along with the other baddies. Leaving the scene of them being arrested by the Arctic Police would have been major lame-o.