Hey Victor,
Welcome aboard and well done on the video and warnings! It seems like you have better connections than us.. female magician-wise.. so please make sure you tell all of them to report him through
http://www.youtube.com/safety_help. Most people on YouTube don't know how to report anyone and just blocking him wouldn't get him removed from YouTube (or Facebook for that matter).
Those messages he sent her are terrible, out of the question. She and her parents could take him to court and have him locked up or force mental health care on him for quite a while for such harassment.