Abaye in the Talmud says: If a scholar is loved by his people it is not because of his superiority but because he does not rebuke them in spiritual matters. (Ket. 105b) It is a known fact that the Rabbis in the Talmud disagree as to whether Noach was truly a righteous individual or did he seem so, only in comparison to others in his generation.
The reason that Noach’s righteousness was suspect was because he had no influence on the society around him. He was notified about the imminent flood and he did not try to change anyone’s behavior. The Torah says: ET HA’ELOKIM HIT’HALECH NOACH, “…Noach walked with Hashem” (Gen 6,9) He was righteous in that he walked with Hashem but he ignored the people around him upon whom he could have had a great influence for good. Noach appeared to his contemporaries as a Tzadik because he did not admonish them.
It is indeed desirable and commendable to be a Tzadik and follow the teachings of our faith meticulously. A person, however, should also be concerned about the people around him. He should also try to see that others are living ethically and righteously as well.