If the world did not know right from wrong then they would have an excuse for their sin, so they could not be judged for their wrong for they do not know better, but all have sinned and come short of the glory of God so we are aware of right and wrong when not saved.
Also creation testifies there is a God, and of His attributes, which one of them is love, and covers the 2 greatest laws, love God, and love people, so the world is without excuse, and covers the whole history of mankind.
Also the secular world has police, and laws, and a person can be in trouble for doing wrong, so they know right from wrong, which God said the Gentiles know right from wrong, and are responsible for their wrong that were not given the words of God.
Of course the non Christian would know right from wrong, for if not nobody would ever become a Christian, for how are you going to repent if you do not know right from wrong.
Bu being led of the Spirit is an advantage to do right all the time.