I have always been amazed at the number of Cinderella type movies that come out every year. One of the things that nearly all of these movies have in common is that the step-mother character gets what's coming to her in the end. Usually, the step-mother experiences some kind of humiliation, often forced to spend the rest of her life doing the kind of back-breaking labor that she had previously forced Cinderella to do. Just as often, the step-mother loses her fortune to Cinderella because it really belonged to her all along. On rare occasions these movies kill off the step-mother character at the end. The reason we always see the step-mother "get what's coming to her" is simple: we enjoy seeing people paid back what they deserve. It's human nature.
Unfortunately, our joy at seeing another person experience well-deserved pain is not something our Heavenly Father is proud of. In the book of Isaiah, God had promised delivery and judgment against the northern kingdoms of Israel and Syria for teaming up to attack Judah. But instead of simply being grateful that God was protecting and avenging them, the people of Judah began to rejoice that Israel and Syria would get what was coming to them. So God sent this message through Isaiah: "My care for the people of Judah is like the gently flowing waters of Shiloah, but they have rejected it. They are rejoicing over what will happen to King Rezin and King Pekah. Therefore, the Lord will overwhelm them with a mighty flood from the Euphrates River- the king of Assyria and all his glory. This flood will overflow all its channels and sweep into Judah until it is chin deep. It will spread its wings, submerging your land from one end to the other, O Immanuel" (Isaiah 8:6-8, NLT).
Justice is important to God, but mercy is just as important, and God's desire is that we crave mercy for our enemies because we ourselves have received mercy. Rejoicing in another's pain or misfortune earns God's discipline in our own lives, no matter how much the other person deserves what's coming to them. When God sees us do things like rejoice over the death of Osama Bin Laden or celebrate that a murderer was executed or gloat that our back-stabbing co-worker had her heart broken, we demonstrate that we do not value justice or mercy the way God does, that we are only interested in payback, and we earn God's judgment ourselves.
If we are truly children of the God who sent His Son to die for a world that rejected Him, our prayer would be for mercy; we would long to see the wrong-doer changed by the Spirit of God and the power of the Gospel; we would find ways to reach out to them just like our Father reached out to us. Even if they deserve it, we should never rejoice that someone got what was coming to them.