Ilion says that I haven't really addressed his argument for capital punishment. It looks like it goes like this.
1. Any civilized society stands in need of protection.
2. The protection of society requires the preparedness to use deadly force. An example would be if, actually happened in 1966, someone went up into the bell tower at the University of Texas and started shooting people. He had to be shot down out of the tower to protect the student and staff of the university.
3. Therefore, a systematic rejection of deadly force in the protection of society undermines the very idea of protecting society.
I think this is a good answer to a simon-pure pacifism. However, someone could argue as follows.
1. The use of deadly force should be used only as a last resort.
2. In the case of captured criminals, deadly force is never a last resort. It is always possible to lock these people up and throw away the key.
3. Therefore, the need to protect society may require the preparedness to kill in some cases, but does not require the preparedness to execute.
It could further be argued that if we have the capacity to imprison for life, this is preferable, because of the possibility that always exists that exculpatory evidence may subsequently emerge.