Ok I think the problem here starcraft is that you're somewhat arguing two points. In the situation of a court case against CoS I would agree they must be allowed to know their accuser. But that has more to do with the implications of such a courtroom situation and the ramifications such a case could have for CoS as a direct result of the court's actions.
In the case of a protester its not their job to provide evidence of wrongdoing or to enforce justice they are simply attempting to bring awareness to the issue. Which is somewhat ironically at odds with your argument against their anonymity. As an example I was discussing this with my mother the other day who in her 50s has taken to being quite politically active. She listens to radio in her headphones, while browsing the blogs online and watching the news on TV. We are talking about someone VERY connected to news...and yet she hasn't heard anything about Anonymous or even really anything about CoS recently.
The irony here is that these protesters wish to bring awareness to the issue yet you would have them remove the mask before awareness is achieved with the reasoning that the awareness (that isn't there yet) will protect them. I think its important to realize just how much is going on in the world and how little this effects most people and how quickly these stories are buried and forgotten. Similarly both of my parents who I saw this last weekend at my brother's engagement party had never heard of Operation Snow White which is the single largest infiltration of our government....ever. I don't think you had heard of it..and I hadn't....and that is directly at odds with this idea that somehow the deeds of CoS will be known should they act. Their deeds most likely won't be noticed, if not because of lazy media coverage then because they've learned how not to get caught. But as Operation Snow White shows even when they do nobody really hears about it.
To bring this debate to a single area I must say that I believe your courtroom analogies are completely irrelevant given this is not a court case. When in court you submit yourself to the judgment of the court and as such rules and rights are established to protect people. But in this situation CoS is not bound to abide by anything the protectesters say and truthfully the protesters have no right to do much of anything but speak out about this. I think the only relevant argument you have is one born of moral right to face your accuser, and while legal proceedings may have been modeled after such moral rights they are far more stringent as a direct result of the abilities and powers vested in the court, abilities and powers protesters do not have.
If you don't disagree with that I would like to focus on the moral argument. Honestly the moral argument is far more valid, especially since this is an international issue and laws are bound by borders where morals, generally speaking, are not.