I’d say Graffiti as “Art” is meant to be a transitory thing, it’s intended to be a temporary statement, graffiti isn’t meant to have preservation orders, assigned “Value” and protection, the Artist typically knows and accepts this, Banksy is no different.
It’s mostly the chattering classes who’ve made his work “Valuable” seeking to preserve and ultimately flog it to one another… And in the process almost entirely missing the point…
The whole point of his work is to make a statement and provoke thought and conversation a picture paints a thousand words and all that.
The fact that it has been removed has done just that, it no longer needs to exist, in fact painting over it has helped drive the point home… Shines another spotlight on the kippers.
Having a piece of work removed by the authorities, that pokes fun at a bunch of xenophobic bigots who are in the process of laying claim to some of that authority is about the best result Banksy could have hoped for IMO…