That's not how the "criminal justice system" works. Not in the US and not in most of the rest of the world, especially the "first world"/"Western world".
Prisoners are NOT release only once they are deemed no longer dangerous. They are release once their allotted prison time is over. They can still be dangerous and released, and they can be not dangerous at all from they one and still go to prison.
Also: Choosing to like someone and dislike someone else, choosing whom you assist when not obligated by law and whom you don't, choosing who gets your time and who doesn't - all of this is not part of the punishment people are sentenced to by the state court system and thus it is not "over" in any sense or way once they are release from prison. You, I, and Mr. sowwww are free to volunteer our time, money and efforts towards whom and what we'd like and we're under no obligation to assist people we don't like just because "they have served their sentence and their punishment is over".