And here you presume that putting someone who commits a capital crime is repaying evil with evil.

I don't see it as repaying evil with evil.  Evil was when the person committed a capital crime and took someone's life in cold blood.  Evil is what that person by extension did to the loved ones of that person.  Restoring justice is a good. Because the death penalty seeks to restore the balance of justice, I do not see it as evil.  I see it as a good.  Given that the death penalty also seeks to protect society, again, I see it as a good thing, certainly not evil.  

In the abuse scandal, people ask why the church sympathized with priests over their victims.  A fair question.  Why do anti-death types not sympathize with victims? 

You mean to tell me that the teenager who killed a man in cold blood--right in front of his children--after he pleaded for his life and his children--does not deserve the death penalty?  Sorry---we are not on the same page if you don't. Victims matter.