My advice is for a slightly different style of conflict than existed there. As for evidence... I can't exactly provide case studies with control cases. I can only point to places where somebody violated the rules, and something bad happened.

There, the issue is more straightforward: It's a blackmail game. Each step enables the next. The first mistake is always standing out; the local fame they develop makes them stand out, which makes them targetable. The second mistake is responding to the first blackmail attack, the DDoS, by adding them as a Skype friend. Then the requests escalate, and previous granted requests provide material for more transgressive requests (personal information obtained from Skype profiles can then be used to dox them, or to gain account access somewhere else, which can be used to blackmail for nude photographs, which can be used to blackmail for... whatever is next in his escalation scheme). It's an escalation game, and the sooner the participant gets out of it, the better off they'll be.

So - reject the very first request. Don't agree to Skype him.