I think it's more a communication problem than a question of rules or behavior (which is why I also disagree with the article's take) People react strongly to

I think it's more a communication problem than a question of rules or behavior (which is why I also disagree with the article's take) People react strongly to "I'm Sorry Dave, I'm Afraid I Can't Do That" types of messages, and the exit command one is pretty close to that. If instead they went for a more question like "unrecognized command. Did you mean 'exit()' ?" type of prompt users would react in a milder way. In particular, choosing an imperative tone in help messages is probably not optimal.