Ah. Ok. So is it ok to hack a malicious hacker to get him/her to stop hacking people? I'd still say yes.
In this case, you become nothing more than what he or she is: a hacker with malicious intent (as per www.dictionary.com, malicious is defined as deliberately harmful). While your cause is good, it is still a malicious in nature. I think it was Negative that put forth suggestions on how to deal with this.
Although our normal reaction to things "bad" is to fight them, we have to step back sometimes and let those in "authority" know about what's going on. Probably the best example of this kind of activity is Cliff Stoll's "The Cuckoo's Egg", where he tracked a hacker for well over a year. He could have at any time taken retaliatory measures even when the "authorities" refused to accept that this hacker was an issue but he didn't. He continued his compliation of information.
I suspect that the actual act of compiling of the activities of the hacker is the best thing you can do against the hacker. One of the hardest things for most authority types is to get proof of hacking activities.
Anyways, that's my thoughts (again!) =)
