I've just copied your comment, but I nevertheless think that it is of low value (as evidence against your hypothesis, I present the case of myself copying your low value comment...).
Proof by recursion!
Exact same reason parody is cool.
However his quoting of it would probably fall under fair use, even though he copied all of it.
[1] http://www.lettersofnote.com/2010/07/i-hear-you-like-tomato-...
I agree that "artistic value" may be a hard defense in court, but the paintings are not about soup. They are about us. The things that we create and our ideas on culture and society.
See Duchamp: [http://en.wikipedia.org/wiki/Marcel_Duchamp]
"The creative act is not performed by the artist alone; the spectator brings the work in contact with the external world by deciphering and interpreting its inner qualifications and thus adds his contribution to the creative act." - Marcel Duchamp