Let us suppose we are an image hosting site, that has in the past been used to host child porn (Think Flickr or ImageHost).
By the same logic, it would then be appropriate for us to maintain copies of child porn in order to filter new uploads against it.
In my opinion, the only organizations that should be allowed to retain copies of c.p. are those government organizations actively involved in policing it -- regardless of motive.
So when our company gets v&, do you think they'll accept our filtering excuse?
Notwithstanding that the IP laws are screwed up, It was still an illegal copy, and I feel the author's case has merit.