It's impossible to comment on this case specifically, because - as squeaky says - we don't know what he actually did!
But generally speaking, I think that if someone has done something that it could be argued makes them a person who may pose a danger to a vulnerable person, then that vulnerable person or a person who is responsible for them, should be made aware so that they can make a choice - to have the person in their life or not, to take precautions or not. To listen to the details and say "so what?" or not. It's about making informed decisions.
When the person who may pose a risk to a vulnerable person is in fact the person who is responsible for them, then how do you safeguard that vulnerable person? Remove them? Or make them aware of the facts and let them make an informed decison? Or let them know of outside support and advice?
Should people generally - not vulnerable people who are associated with the offender, but general family, friends, neighbours etc have the right to know if someone around them is a criminal? Well, on one hand, if you knew that the person who lived next door to you was a serial burglar, for example, you may choose to get a better alarm system. If you know that a family member has abused young children, for example, you may choose to ensure that your own children are not left with them. etc etc. You can make informed decisons. You can risk assess with all the relevent information.
However, this relies on people being reasonable and not pitchfork wielding idiots. Which is a problem, because many people are not reasonable and are only ever a hair's breadth away from grabbing that pitchfork. It also causes a problem for the offender, who may want to change, but people will always treat them as though they are committing offences. So they may never get a second chance. And if people have already condemned you for life, where's your incentive to change?
So I think, on balance, that you should risk assess and give careful consideration to informing vulnerable people and their advocates if it is thought that there may be a risk to them, but other than that, people shouldn't be informed.