The majority of released child sex offenders
don't re-offend. Partly because most child sex offenders are family member or friends and when the children they attacked grow up they don't have further opportunities to offend.
It seems to be popular to imagine that child sex offenders are a uniquely terrible kind of offender but for the most part that's not true. Repeat and unrepentant offenders like Glitter deserve to spend their lives in jail - for the protection of others more than anything else - but he's the exception not the rule.