Saving Banksy is a documentary about the value and purpose of street art/graffiti in modern society. Yes, the documentary deals with Banksy's work, but the actual scope goes far beyond the specifics of one artist. It's largely a discussion about context, artist's intent, ownership in public spaces, and the gatekeepers of what is or isn't worth being preserved in art.
The narrative of the documentary is straight forward but not simple. In 2010, Bansky, the secretive graffiti artist known for his political and satirical work in public places, produced six pieces in San Francisco. San Francisco had laws in place that would fine building owners who did not remove graffiti from their walls in 30 days. Five of the pieces were destroyed within days of being put up--other graffiti artists tagged the pieces or the building owners cleaned off or painted over the work.