Answer:
Respect all ideas.
Explanation:
This group Norm was Broken, because this person hurt the feelings of the one who spoke the idea. The answer could be Don't Interrupt, but the reason why it's not that, is because He didn't interrupt, it says that <em>after</em> he was finished, he said it. Hence, your answer is "Respect All Ideas."
Thanks!
If anything, it made it a bit more frightening... It gave the reader access to his insane mind.