Using "natural states of being", however defined, to articulate rights in unnatural states of being (i.e. modern society) is a fallacy. It presumes that a natural state of being naturally endows people with all their rights, and that the arbitrary social systems that have evolved on top of that natural state have systematically deprived people of those rights. In some cases, this has happened, but it is not an inviolable law.
For example, in the "state of nature" women are born weaker than men, but that doesn't mean that men have a right to drag them back to the cave and do what they want with them.
> "Society has weighed the pros and cons and decided that this particular set of technologies is on the whole good. That it might in fact want to limit the level of anonymity on the network seems reasonable, in the same way that making people put license plates on their cars is reasonable."
"Society" is not a monolithic, homogeneous organism whose will is absolute and omniscient. Society is composed of many subcultures with differing ideologies that change over time. "Society" has not decided to "limit the level of anonmymity" on the internet; it is only some factions within it that believe that should be done. The worrying aspect is that these factions often promote it as a public good (using the same "societal consensus" language you have invoked) that only fringe groups like terrorists and pedophiles oppose. As long as indifferent factions (which most ordinary people fall into) are more swayed by this kind of fear mongering than by a desire to prevent the machinery of the destruction of their rights from being built, the minority faction that argues that privacy is unnecessary or even dangerous will exert a disproportionate level of control over our entire society.