I understand all your points, many are valid and people can falsely accuse others, BUT, the reason the sex offender registry cannot be outlawed is that our children as well as ourselves have the right to know who has been labeled a potential risk to their life, for their own safety. We too should have the right to know who could hurt our children so as to not to attract those people into our lives.
But many modifications to the laws are needed as well. Falsely accusing should be criminalized and punishable by jail time so that on one has the right to or desire to falsely accuse another. Also, if a minor admits that she lied about her age and/or lying about age can be proven in court then the accused should not be punished at all.