Agreed. The guy is a moron. This is like sending a prize dairy bull to the slaughterhouse. But if it is your bull, I guess you have the right to be a moron.
I had no idea how much these Banksy murals can be worth. The property owner may have painted over half a million dollars in market value:
http://www.widewalls.ch/10-most-expensive-banksy-artworks-at-auctions/