"We are honest people" (Gen 42:11) Just as Jacob had no idea about what he was wrong at the beginning (because he was essentially wrong about himself, not about some detail), so his sons consider themselves "honest people." How is it possible that those who almost killed their brother out of grudge and when they did not kill him, at least made him a slave and deprived him of his family, homeland, property, rights, and the whole future, call themselves "honest"? How could they live with the lie that had almost ruined their father and watch him suffering because of it all their lives?
A man can calm his conscience by judging himself only in the areas where he knows he does not fail and remain in blindness regarding the other ones. That is why our world is full of "honest people" and many of them, like Joseph's brothers, have their small (for all cases) religion.