What’s the Use?

Psalm 109: what’s the use?

“He who falls upon the Rock will be broken, but He upon whom the Rock falls shall be ground into powder.”
One can safely assume that each Psalm has an important message for the modern believer. But what are we to do with Psalm 109? One of the most breathtaking curses in Scripture, Psalm 109 is awe-inspiring in its mercilessness, breadth and utter contempt for the enemies of David..
Is this scripture a green light for believers to possess the gates of their enemies or a red light, revealing the excesses of an Old Testament Jew? Did Jesus ever read this part of Tannach or did he write it?
This is a psalm about people whom David loved and treated well at one time. It concerns people who responded to David with hatred, deceit and lies. In response, David does not address his unfaithful friends, but cries out to Yahweh for justice. He then begs God for the mercy and blessing he would deny to his adversaries.
David sees Yahweh as the savior of the righteous, the deliverer of the afflicted. He declares the LORD stands at the right hand of the poor and oppressed. David does not waste time comparing his own sins to those of his enemies. Crying out for mercy for himself, he focuses the attention of God on the hearts of those who hate him. 
“For Thy name’s sake,” David cries, “curse those who afflict me.” David defines his enemies as enemies of God. He so identifies as the chosen of the LORD that he reminds HaShem that what these ungodly men are doing is directed against the Living God, Himself . 
Is this the Christian thing to do? It would seem so. after all, Christian means little Messiah. It was Jesus who said, “Those who give mercy will receive mercy” and “as you give so it shall be given to you, pressed down and shaken together.” These words are for the merciless as well as the merciful. Jesus does not ask His Father to be merciful to the merciless nor does he bring good news to the arrogant and haughty. 
What He does bring to sinners is a bright line in the sand. He declares He has not come to condemn the oppressor, the sinner and the wicked because they are already condemned by Yahweh. “This is the judgement of God,” declares Messiah. “Men have chosen darkness rather than light, because their deeds are evil.” Instead, He offers all those who are courageous and humble enough to face their sin, and throw themselves upon the mercy of God, the power to become the children of the Living God of Israel. To the rest, as David did before him, Jesus says, “Have it your way.”