Everyone will have their own code of ethics, no matter how strict or loose. The majority of the people in a culture will have similar ethical codes that are shaped by that society's standards and laws.
Truth is an ever-changing idea written by the popular culture.
It used to be true that Europe was on the big continent and you could sail around the world and reach Asia. Then it was true that Christopher Columbus discovered the Americas, disproving the old truth. Now it is true that the Vikings reached and colonized North America long before Columbus was even born. I think that the codes of ethics are meant to protect the journalist. They are a sort of ethical checklist to refer to.