What does Psalm 4:2 mean?

The background of this psalm is the same as that of Psalm 3: the violent rebellion against David's rule, by his own son, Absalom (2 Samuel 15—18). In this verse David turns his attention to Absalom's followers. He asks them two questions: How long will you tarnish my reputation? How long will you follow lies?

These men had rejected David's rule because they allowed Absalom to deceive them. Absalom's good looks and flattery persuaded many people to reject David, instead supporting Absalom as king. Second Samuel 14:25–26 says, "Now in all Israel there was no one so much to be praised for his handsome appearance as Absalom. From the sole of his foot to the crown of his head there was no blemish in him." Absalom also manipulated popular opinion. He had fifty men run ahead of his chariot. He also sat by the city gate and expressed judgment in favor of anyone coming to the city for judgment in a dispute. Absalom told them their claims were "good and right," but that there was no representative of the king to hear the dispute; he claimed if he were judge everyone would receive justice (2 Samuel 15:1–5). Absalom successfully stole the hearts of the people (2 Samuel 15:6).