Which is why like some states, there needs to be levels on the registry. Highest level offense is a predator not just an offender.
The problem is where the line should be drawn. Obviously murderers should be put to death. The problem comes when the lines aren't so bright. Should a teacher who is acused of raping two students face the death penaltiy if convicted? What if the case is based solely on the students word against the teacher?
The other question is whether a predator is more likely to kill his victims if he knows he will die if he is caught? Unintended consequences rears its ugly head when emotions come into play.
So yes having different levels of offenders is probably a good Idea. Simply killing the offenders may not be such a good idea : )