In his commentary on Psalm 64, James Montgomery Boice said: "It is not very often that David finishes a psalm without mentioning his enemies." It doesn't take a very in-depth study of the psalms that David authored, to see the truth of that statement. David's enemies seem to have been a very persistent part of his every day life. It appears that his entire life was a series of conflicts with those who, through ceaseless verbal, political, and physical attacks, sought to either destroy or depose him.
Of course, we would expect a man in his position to acquire a few enemies along the way. He doubtless produced a few enemies through the wars he fought against rival nations who were the perpetual enemies of Israel. He had political enemies as every leader has, and he also garnered some hard feelings through his own personal failings.
All of these types of enemies we can easily understand. However, David had other enemies too. People who should not have been his enemies at all. They had no reason to hate or oppose him at all, but they did. Many who should have respected and admired him, despised him. I say they should have admired him because there was much about him to admire, regardless of his short-comings.
For the most part, he had been a careful man. He was called "a man after God's own heart", and most of his life, he lived in conscious awareness of God's presence. He was a brave man. He courageously, and selflessly, as mere youth, went against a lion and a bear to protect his father's sheep. Again as a teen, he fought and defeated the giant, Goliath, who had caused the whole Israeli army to cower. He did it single-handedly believing that the battle was the Lord's. When Saul became jealous of him and sought his life unjustly, David would not avenge himself nor take advantage of multiple opportunities to harm, capture, or kill him. He preferred to let God take care of Saul in His own time and in His own way. As king, rather than seeking the destruction of Saul's family, he sought to show them mercy. Also as king, he brought the Ark of God to Jerusalem and openly worshiped God.
These things should have sparked nothing but respect from all those who witnessed them. However, not everyone was impressed with David's spirituality. Some actually hated him even more because of it (Some of them from his own family 2Sam.6:14-23). How can that be? Here is where we can learn something about many of David's enemies as well as our own. They had no reason to hate him except for this fact: In their own hearts, they were at war with the God that David so passionately worshiped. Their problem was not with David at all. Their real problem was with David's God. So, they attacked David with all the pent-up resentment with which they would attack God, if they could just get at Him.
That's how it was then and that is how it is even now with modern-day saints. There are people who are in rebellion against God(Often they are of our own families Matt.10:34-36). They don't like His authority, His demands, or His ways. They would attack Him personally if they could, but they can't. So... they attack those who love and serve Him, and the closer to God you live, and the more fervently you serve Him, the more stubborn will be the opposition.
Jesus articulated this principle in Jn.15:18-25, then He lived it out before the very eyes of His followers just a few hours later. Neither Rome nor the Jews had any reason to hate Him, but by their unreasoning determination to brutalize, torture, and crucify Him, they put on display, for all the world to see, their deep, cruel, and abiding hatred for God. Someone has described what happened at Calvary by transposing the words in the title of Jonathan Edwards' famous sermon "Sinners in the Hands of an Angry God" like this: God in the hands of angry sinners. That makes my point perfectly.
Christ on the cross was, on one hand, God's goodness, God's mercy, God's love in it's most magnificent display. On the other hand, it was man's depraved rebellion against God in it's fullest revelation. This explains, at least to my satisfaction, why even the sweetest of Christians have enemies. Our enemies are real, their attacks and abuses are painful, but we must remember that their issue is with God. Therefore our response should be to:
1: Love them
2: Do good to them
3: Pray for them (Matt.5:43-48)
If anything else is required, leave that up to God. After all, the battle is the Lord's.