By saying clearly different, I don't mean to minimize the actions of the vigilante. One of the chief characteristics of civil disobedience, for example, is to resolve that could it be question. By receiving the unjust punishment the dissident displays good faith with proponents and opponents. I don't yet see how pseudonymous hacktivism keeps that good faith with the public. And that seems to relegate it either be small scale, symbolic acts like this or large-scale grey hat stuff that brings lots of unwanted risks/cooptation/etc.
It's actually the main relevant part of the analogy.
It goes to veracity.
There's a person who gave a public talk about manipulating Bitcoins with weak private keys in order to alert the owners that they were vulnerable. But he did it in a way that verified to the owner he hadn't in fact stolen the coins (moving small portions around or maybe signing with the key, I can't remember). He also mentioned in the public talk that the owners of those Bitcoins were totally freaked out by this, and most were never convinced that he was acting in good faith (which is probably a smart assumption on their part).
So the fact that he didn't steal the coins is completely relevant-- it's the very reason he could give a public talk on what is still grey area behavior.
Your hypothetical thief, on the other hand, is clearly mendacious. You have him claiming, "If I don't capitalize on it, then people won't understand the costs/risks." That is clearly false from my real-world example above, and if he tried to give a public talk about how his theft benefited society he'd be arrested.
Your point that I couldn't have given a public talk had I stolen the coins is completely correct. I still spoke with a lawyer about it ahead of time, though. :-P
There was another person, who was somewhat less scrupulous, who would simply steal the coins and watch for someone to complain in public about it, then offer to return them. They use a pseudonym and as far as I can tell have vanished.