I used to more or less oppose the death penalty for reasons you have identified. I felt like life in prison was a sufficient punishment. I live in Oklahoma City, and after the bombing I toured "the fence" that had the "lives" of people that were now dead attached to it. Everything inside me understood that the death penalty is appropriate in some instances.
Unfortunately, I think Christ left a mixed message. For those of us who wonder about whether the death penalty is appropriate, John 8 seems to support our belief. He actions clearly spared that womans life from what was believed to be the remedy for her sins under the law. For those who believe that Paul's discussion of the civil laws in Romans (where I believe he does draw a line between civil and Christian) and the fact Christ was mute on the cross when hung with the two thieves with regard to the penalty, they hang their hat on those passages.
Again, a mixed message.
I personally do not believe in the death penalty either, as I do not believe humans have the right to take the lives of other humans, however it is the law of the land and this man certainly did not deserve clemency from it any more than any other death row inmate. This man laughed about shooting an innocent man to death while he begged for his life-one does not "redeem himself" from something like that by writing a couple of books.
Incidentally it never fails to leave me incredulous that all of these hypocrite liberals singing and begging to spare the life of this violent animal are all for allowing a woman to shred an innocent baby to pieces for any reason whatsoever. Last night Alan Colmes said "Yes, I am pro-life but I'm also for a woman's right to choose". Blechh.