I'm not denying ability to reform to anyone, they just will have to forthcoming about their past and persuade the other party that they have changed and to give them a chance. Definitely better than for instance giving child molester chance to molest another child, defrauder to defraud another victim and so on.
I think child molestation and other sexual offences are normally dealt with via alternative means. In the UK there is a sex offenders register as well as background checks for people working with children etc.