"Does such a society exist today?"
Good question. It's certainly been an ideological goal and philosophical debate for many centuries, it forms part of the basis upon which the democratic system was founded, but we are still striving for such a society today, and for how much longer?
It is true that dissemination of sensitive data can endanger those to whom the information relates, but it doesn't need to be publicly released in order for their to be a safe means of raising the matter of concern without prejudice or persecution.
"...who gets to decide?"
About what, the release of information/allegations, the final assessment of its legitimacy? I don't understand the context of your question.
Great points, this is the kind of discussion that needs to happen openly and often.
By "who gets to decide," within the context of:
Layer upon layer of safeguards and representative members seem to breed bloated bureaucracies. Trimming the fat could still provide the safe means you speak of, however I doubt the chances of that happening.
Simply put, who watches the watchers.
I agree, critical thought (which your post certainly requires!) and discussion need to happen. These are difficult topics and in my estimation missing between the general public and those chosen to undertake the task.