They have belied the LORD, and said, It is not he; neither shall evil come upon us; neither shall we see sword nor famine: They have belied the Lord - כחשו kichashu. They have denied or disavowed the Lord.
It is not he - לוא הוא lo hu, he is not; there is no such being; therefore this evil shall not come upon us. On their premises, this conclusion was just. There is no judge; therefore there shall be no judgment. Thus they denied the Lord. They were atheists at heart.