if Plato were DRM-ed, the license servers would probably be not available today, and thus the Plato itself. In that regard DRM to today's cultural artifacts is like Alexandria library fire to the artifacts of ancients.
there is significant difference - knowing the format (or even just basic principles of the format like in case of compression) one can restore the content ( http://www.cs.huji.ac.il/~springer/DigitalNeedle/ ), while in DRM case knowing format isn't enough. Another illustration - one can apply some analysis and probably read lost ancient language texts while it is fundamentally different from reading cyphertext even in known language. I.e. DRM is intentionally and explicitly converts "information" into highest entropy content, i.e. "erases" the "information". Basically what flame does to human artifacts.
In this sense, nothing is a "human right" per se, not even not being murdered.
Human rights are what we define them to be.
Now you might change your argument to "it's not a serious enough right".
But in that case, I'd argue that the issue of open access to cultural artifacts, even if it's Ben Stiller and not Plato or the Principia Mathematica, is quite serious matter.