HOW does one learn ethics and morality in a secular world?

So I hear so often, with respect to business (corporations), the term "greed" being applied to the ownership. Although how this alleged greed actually manifests itself in terms of policy is rarely defined, the term is nonetheless used to cast judgment upon a business as operating in a less than ethical manner, of course due to those at the top exercising their greed, apathy or the like. Yet, when I look at society, everywhere I see absolutes replaced with moral and ethical relativism. The tenets of organized religion have been expunged from public discourse, from our schools, media and entertainment, leaving a void. There is no longer the simplistic "good guy" in the white hat and "bad guy" in the black hat. Nowhere from earliest childhood are the concepts of ethics and morality set forth as standards that our children are supposed to emulate for the sake of the civil society. In their place are malleable dogmas of condemnation for inappropriate thought or behavior but those dogmas remain in constant flux and are based on nothing but the fashionable whims of the day. They are rooted in nothingness, no foundational principles. My question is, how is a business person expected to behave in a manner that is considered "moral" and "ethic" when instruction of those virtues are to be found nowhere in secular society. What is the moral argument that greed is wrong and what is it based on? Is that basis solid or fluid? Is that standard across the board or selective in who or what it applies to? Please someone explain the foundational basis of secular morality.