Relative deprivation certainly seems a better explanation than requiring some mysterious "fundamental universal rights" that people never knew they had until 18th Century Westerners discovered them. Maybe they're a bit like "souls" for atheists?

Well, fundamental human rights were, by the 18th century "discoverers", usually attributed to endowment by a Divine Creator, so maybe not particularly "for atheists".

But, yeah, they are certainly non-physical non-demonstrable entities that are presumed to exist based on faith alone.