I would say it expresses that not everyone is evil, though not everyone is kind hearted, so no strangers or most likely anyone can be trusted. Since this is common knowledge, most people don’t engage with strangers, walk in public with caution, and never listen to individuals they just met. This exploits that society has brought us upon a nerve wracking feeling, since the world around us is not safe, and that even uncommon behavior and people who are out of the ordinary, will even be put to a severe punsihment, a death sentance back then, or in modern day, jail.