Good point. God is a God of mercy but He is also a God of justice. They are both sides of the same coin. You cannot have a truly righteous society if it doesn't protect the innocent by severely punishing evildoers. Your observation about the death penalty needs to be tempered with the qualification that it needs to be applied EVENLY. Only the most morally obtuse person could argue Saddam, or any other murderer for that matter, doesn't deserve to be held accountable for his transgression against God. I am of the view that if someone takes an innocent life without justification, like self-defense, that person's own life should be forfeit as a matter of course. A just society is the only one that is truly a merciful society.
"Show me just what Mohammed brought that was new, and there you will find things only evil and inhuman, such as his command to spread by the sword the faith he preached." -Manuel II Paleologus