And how do you know this? Were you alive back then and knew some of them personally?
It is already an established fact the one group of criminals most likely to reoffend are sex offenders. You are going to have a real hard time making myself and others believe when our Founding Fathers wrote the phrase, "Life, liberty and the pursuit of happiness" they were thinking of anally raping a toddler, causing their death and leaving semen in their chest cavity.
And how do you know this? Were you alive back then and knew some of them personally?
Uh, read the Constitution, especially the section about ex post facto laws. The founders wrote that section. Therefore, it is a reasonable assumption that they were against retroactive punishments, without have to have known them personally.
Note that I am not against a registry - just applying the requirement for such retroactively. Personally, I think a registry isn't sufficient - there should be lifetime probation for these perps if they are convicted, and upon second offense either shoot 'em or give them life in prison without parole.