I have no problem executing the ones who kill their victims like this vermin did. The only issue is what method to use. Personally, I would prefer to go back to public hangings in the courthouse square.
The problem is what to do with pedophiles who do not kill their victims. Although I believe that they deserve to die, there must be a greater punishment for those who kill than for those who do not. Otherwise, they will all kill their victims. If the punishment is the same either way, why would any of them allow a victim to live, who can later pick them out of a line up and testify against them?
Erect a very large secure fence and throw them all in there and leave. Starvation is a very painless, euphoric way to die.