‘O you sons of men how long will my glory be turned into dishonour?
How long will you love vanity, and seek after falsehood?' Selah.
This again fits well with David's situation. It was the vanity of Absalom that had finally resulted in the rebellion, as a result of Absalom's false claims (2 Samuel 14:25-26; 2 Samuel 15:1-6). Thus David's glory as king in Jerusalem had been replaced by the dishonour of dwelling as a fugitive in tents. And even more his status as ‘Yahweh's anointed' had been marred by the accusations that had been made against him.
However the words can also apply to any man of God who has been dishonoured because of men's vain thinking and deceptiveness. How easily can a man's reputation be wrecked by lies. For the world hates those who are true to God (John 15:18-19; John 16:2). So Jesus paradoxically warned of the danger of being thought well of, for that too would only result in persecution because of the nature of man. Men hate those who are truly righteous (1 Peter 4:14; 1 Peter 4:16; Matthew 5:11-12; Luke 6:26), especially when others see them as righteous. It was something that Jesus Himself suffered from, as He was misrepresented by the leaders of the people. These words could easily be applied to Him.
‘O you sons of men.' Not ben 'adam but ben ‘ish, high born men rather than low. See its use in Psalms 49:2; Psalms 62:9. His address is to the high born who are responsible for his distress. By evicting him from Jerusalem with the intention of removing him from the throne they had dishonoured him and the glory that was his as YHWH's anointed. But they are still but sons of men, in contrast to God, and they should remember that, for God is not pleased when those He favours are ill-used. And whenever the true people of God are attacked falsely and dishonoured it is God's glory in them that is being outwardly tarnished.
‘How long will you love vanity, and seek after falsehood?' When men attack those who are God's they are revealing that they love ‘vanity', that, is the desire for empty and meaningless things. They are seeking what is temporal rather than what is eternal. And regularly they do it by deceit, as Absalom had deceived. They deceive themselves and they deceive others, twisting facts in order to win their case, erecting a refuge of lies which will one day be swept away (see Isaiah 28:25-27).