Stupid co-worker (spoilers)

Only minor thing that annoyed me about this film was the stupid co-worker. Are we supposed to believe people in Norway have no common sense? How much evidence do you need before you stop trying to get into someone's house? John is asking him nonsensical questions with a crazed look on his face about imaginary apartments next door, is that not enough? You hear someone obviously [spoiler]fortifying himself inside his apartment, isn't that enough for you to stop knocking like an idiot over and over?

I hate these subtle unrealistic reactions much more than incredibly obvious tests of my suspension of disbelief. Like in Japanese movies, where people just stare at things happening while standing around like idiots or when someone is assaulting them and all they can do is whine like little girls instead of defending themselves.

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"Den Gleichen Gleiches, den Ungleichen Ungleiches."