Individual healing is not contingent upon seeing venegeance exacted upon the perpetrator.
The demand for personal exaction of justice only ties the victim to the perpetrator. It gives the perpetrator power to torment you even when he isn't present.
"Forgiveness" (in well-reasoned Christian thought) has two levels: the human and the divine. Human forgiveness is not linked to seeing justice served. Jesus expressed forgiveness from the Cross even though the perpetrators went unpunished (from a human persepective). Literally, forgiveness means "send away." When we forgive, we break the bond that the perpetrator has inflicted on us by his abuse. We "divorce" (another meaning for the greek word translated "forgive" in the NT Scriptures) the issue and break the power of the perpetrator.
The opinion that McVeigh must die so that the families of his victims can be healed is erroneous. Their healing is not linked to his death but rather to their ability to experience miraculous grace and healing.
On the other hand, the divine level of forgiveness is linked to authority, society at large, and the inner workings of the human heart. Here, human government has a role to play, and has the authority to take human life that is guilty of "bloodguilt." This judicious use of the death penalty is not considered "murder", which is what the commands of God actually forbid. In Christian thought, this authority has been bestowed on human government by God himself. Jesus did not contest that authority when he stood before Pontius Pilate, and the Apostles, most of whom were killed for their faith, also taught that human government has this authority. Those in positions of authority will give account for how they use it. The earliest Christians were abused and victimized by unjust use of the death penalty, yet taught that government had the right to use the death penalty in certain cases.
Corporate punishment is intended to encourage individual responsibility and deter abuse. When held accountable for my own bloodguilt, I am more likely to deal honestly with it and possibly experience divine transformation and forgiveness.
On a more personal level, leaving the "Christian rambling" behind, I am deeply troubled by the prevailing thought of many that McVeigh had to die in order to bring healing to the victims. I do not deny the government's role or existence of the death penalty as a means of restraining human lawlessness and holding people accountable for heinous crimes against humanity. Holding one accountable is one of the best ways to enable the deliverance of that one's soul.
But my choice to forgive and "send away" the wound and be healed is not contingent upon anything that the perpetrator does or anything that is done to him.
The only person guaranteed to be healed by forgiveness is the one who forgives, and that grace of forgiveness is open to all who will choose to walk that narrow road. It is not dependent on anything anyone else does or anything that is done to anyone else.