Capital Punishment Requires Belief In Absolutes
You leave out an "absolute." The idea that it is absolutely morally wrong to kill someone when it can be avoided. A sentence of life imprisonment without any possibility of parole at any point in life would be a substitute for the death penalty, and would successfully protect society from the dangerous offender without the need to kill him.
Real Clear Politics...isn't it funny...
RCP uses only the most recent poll from each pollster in calculating their poll average. The latest Wash post poll, the latest Ras poll, latest SUSA poll, etc. There is no bias in their averages. They may use an imperfect model (it can be argued) but their poll averages are based on that predetermined model, not some person's opinion that could introduce bias.