Why did Klaatu come in the first place?
The "alien council" already decided to destroy the human race. They are collecting samples etc. What is he doing here?
''they should have a spell check button for non-native speakers''
No, he was the deciding factor on whether humans need to go or not.
That's what the entire scene in McDonald's was for; Klaatu getting the opinion of the old Asian man, and him deciding to rid the planet of humans.
Warning, I'm a one.
Near the very end, the boy did say something like, "No, he stopped it".
I thought they may have been implying that he was 'God'.