God says we must forgive those who wrong us, thats a non negotiable if we dont then we cant be forgiven, simple as
that said if my abuser was still alive today I would make it quite clear to him that he was forgiven however I would not put myself or anyone I knew in a place where that man could do the same thing. we have to forgive but we dont have to put ourselves or those we love in a position where it could happen again
If they are non repententant I would simply remind them that "all have sinned and fall short of the glory of God, and that the legal age for sex is 16 and if they dont repent, they are in hot water" and yes I would probably be that flippant