The child molester is pretty much on lifetime probation which means that criminal act has different consequences than someone who committed a crime, did the time and finished parole.
No, once off probation then a child molestor's "debt to society" is paid. But as long as he lives he is on a registry. He can't live within a certain distance of a school or daycare. He can't do a lot of things. He is punished for the rest of his life because he has shown he can't be trusted around kids. So why is it different for a murderer or armed robber? Having shown that they will abuse the right to own a gun by using it to commit a crime then why should they be trusted again?