Of course killers deserve to die. Rapists deserve to be raped. Batterers deserve to be beaten.
Thieves deserve to be flogged.
You won't get an argument from me there. But our courts and our Constitution generally look to other sorts of standards and questions when considering the administration of justice. I do not accept execution because it is an equivalent response to murder. In fact, the act of murder is so overwhelming that execution cannot truly be considered justice, but simply the only degree of justice available on Earth. While you believe that rapists deserve to be raped, such finding for equivalence is misplaced.