Firstly, M&B forum definitely isn't the right place to make such a post. If you feel like there is an event of cyber-crime you should report it to your local authorities instead, with all of the evidence.
Secondly, you talk about him a lot and it seems like a person who you have personally known. In that case, have you attempted to talk to him about this? Perhaps he's been abused in his childhood as well, or maybe he has a particularly tough life? Talking bad about people is always the easiest, but have you considered helping instead? Whilst it is not my place to talk about such issues (as I have no experience-based or academic knowledge in this area), a quick google search yields: "Many people who identify pedophilic interests often want help but don’t know how to ask. Sometimes they may leave clues in order to get caught, as they don’t know how to talk about something so personal or private."
Finally, if it is indeed an issue of paedophilia, blackmailing, and other, rather *evil* topics, please try to keep the privacy as high as possible, especially in the case of the victims. Sharing names, nicks, and locations is not essential.