Comment by tptacek
"To be improper, interference must be wrongful by some measure beyond the fact of the interference itself, such as a statute, regulation, recognized rule of common law, or an established standard of trade or profession."
They don't need a defense: nobody has yet stated a claim!
It was claimed they committed copyright infringement and they admit to photographing his works as part of this discovery.
It actually being copyright infringement is questionable, but if so it would be improper behavior.