Moral is defined as being in accordance with or concerned with right conduct or its principles; conforming to these principles rather than to law or custom. Morality is an internal compass which points us in the direction of right or wrong. As humans, we are not born with this knowledge, it is taught to us by our family, friends, and culture. A government or community may impose moral standards, but ultimately these values are unique to each individual. Therefore, what was immoral to Freud, may not be to other people.
Freud states that human beings have certain moral instincts that would guard against a crime such as marrying one's mother and that the Gods deceived Oedipus. This deception allowed Oedipus to believe his marriage to Jocasta was legitimate. However, the play leads the reader to believe that Apollo did not plan this deception. The plague is sent to punish the land of Thebes because of the actions of Oedipus, primarily the murder of King Laius.
Although human beings may have Freud's moral instincts that offer some protection against this type of conduct, we cannot apply those to the character of Oedipus. Oedipus had been deceived about his lineage, either by the divine intervention of Apollo or his own bad luck. He believed his true parents were Polybus and Merope from Corinth. To the best of his knowledge, Jocasta was not related to him