There's only two ways of defeating a stalker.
1. Put them and all their nicks on ignore and/or simply don't reply to them in any way. Most will get bored with knowing that it appears that their efforts are not having the desired affect. If you reply to them you are giving them the satisfaction they want.
2. If the person is dangerous, ring the police. I don't support online 'net coppers'. Sites that offer advice are fine providing the site is authored by someone that lives in the same jurasdiction as you but sites promoting a type of online law enforcement are not and for a number of reasons.
Firstly and most importantly the law depends entirely on where you live. What is quite okay in one jurasdiction is not okay in another.
Similarly some jurasdictions allow vigilantes to enforce the law whereas others do not. Countries and states that operate to "Common Law" principles will not allow it because in most cases a normal citizen doing crime fighting is interpreted as stalking in itself which is why in most cases people such as security officers and private enquiry officers have to do a course and then hold a licence.
At the end of the day, take it from someone whos had everything from "I'm a h4x0r and I will own your box" to phone calls mentioning my full name, followed by the death threat and how it will be carried out, just ignore the idiots completely and they'll go away.
