The people responsible for checking tickets of the passengers. Their culture, patience, and refinement oftentimes is inadequate towards commuters who simply left the electronic card of paper ticket back home.
Is it possible that North Germans who would quite happily submit to angry, sarcastic and rude questioning from another North German as long as he had a badge and a peaked cap, feel that it's below their dignity to be treated in exactly the same way by someone of 'Mediterranean appearance'?