ave you ever put salt on a snail? Supposedly, the snails do not technically melt, but it sure seems like they do. And while that might be an interesting exercise for a curious young boy, it sure sounds strange when we read in Psalm 58:8 that David was praying that wicked men would melt away like melting snails. Yet this is only one example of the harsh ideas that David postulated as "good" plights for evil men. "Break their teeth, cut them in pieces and let them die in obscurity... unknown and ignorant. May the righteous wash their feet in the blood of the wicked" - these were the sentiments of David as he wrote this psalm.
One might claim that David was guilty of dehumanizing his enemies in order to feel better about seeking their obliteration. I think David would retort that they were guilty of dehumanizing themselves (Ecclesiastes 7:29). It is true that he called them "deaf snakes" and "adolescent lions," but were they not living just about as wildly as those beasts do? If you don't want to be treated like a wild animal, then don't act like one.
Frankly, David had vengeance and emotionless justice in mind when he wrote this Psalm. His main concerns were that (1) people would be willing to admit that moral men will eventually be glad that they picked the right path, and (2) that God's reputation (as a Judge with perfect character) would be preserved.