It has, it would seem, ever been thus. The heaven he proclaims does not include, as part of its joy, the emotional pleasure of watching the suffering of those who made us suffer. This execution is wrong, not because it might serve to make Timothy McVeigh a martyr in his own eyes, but because all killing is wrong, pure and simple. Killing begets more killing and violence begets more violence, always. There's a circle of death, just as there's a circle of life.
Capital punishment is part of the circle of death.
There is no morally superior violence. Capital punishment abdicates its moral ground precisely because it mimics, however unconsciously, the very violence it's sincerely trying to subdue. Killing is killing, no matter who does it. Jesus wouldn't pull the switch on a death-machine and we shouldn't pull it in his name. He tried to use a violence he understood as being morally superior to make a statement.