Since when do murderers, rapists, terrorists, etc actually change their ways? They don't. Why bother spending money and space for them to go to jail when we can just simply put them down. Put them down with a firing squad and I could care less, plus ammunition is cheaper then using some stuffty drug that takes an hour to kill them.
I don't think terrorists are as bad as murderers. I might explain this later. Firing squads are better than lethal injections. They are less painful and cause less emotional trauma for the person, and they are a lot cheaper.
Nobody is trying to rehabilitate murderers. (Lots of rapists have been rehabilitated, you are wrong.) Its only a matter of whether it's life in prison or death.
You know what's disgusting? When someone rapes and kills your family. Those are the people who deserve to die. You only get the death penalty if what you did was considered cruel and unusual.
Society should not work on an "Everything must be equal" system. If you do exactly what a murderer did to them, you are no better than they are. Mercy is what makes people rise above killers. Mercy is much more important than revenge.