Please Help me understand.

Ps. 52:6 The righteous shall see and fear,
and shall laugh at him, saying,
7"See the man who would not make
God his refuge,
but trusted in the abundance of his riches
and sought refuge in his own destruction!"

I am having a hard time with vs.6. I don't want to make myself out to be overly compassionate, as I have a long way to go in this area, but it does seem a little rude, or in poor form, to be laughing at someone who has not been shown grace. There are many times that David is praying for the destruction of his enemies and I am wondering if this is what God desired for him. I really don't know the answer to this.

Matt. 5:43 "You have heard that it was said, 'You shall love your neighbor and hate your enemy.' 44 But I say to you, Love your enemies and pray for those who persecute you, 45 so that you may be sons of your Father who is in heaven. For he makes his sun rise on the evil and on the good, and sends rain on the just and on the unjust.

How do we reconcile this with many of the Psalms of David? In my flesh it would be easy for me to pray harm toward my enemies, but I don't think this is what God wants for me.

Please give me some of your understanding.