Digital goods are fundamentally non-excludable and non-rivalrous (sometimes anti-rivalrous, as with software). Thus the semantics of "theft" do not apply. At worst it would be free-riding, which has different implications.
Face it, you're a fringe view.
The code is:
> Whoever transports, transmits, or transfers in interstate or foreign commerce any goods, wares, merchandise, securities or money, of the value of $5,000 or more, knowing the same to have been stolen, converted or taken by fraud; or ....
The semantics of "theft" absolutely do apply
Definition of theft: the act or crime of stealing.
Definition of steal: to take (something that you are not supposed to have) without asking for permission. http://www.merriam-webster.com/dictionary/stealing
So the people trying to get through the not stealing it is copying due to a technical definition of theft are wrong. Stealing is having a copy that you didn't get permission to take.
My other ethics brain is wondering how NOT taking property but a copy seems to also allow sneaking into a movie theater, concert or sporting event to watch something. You are neither taking anything or even copying you are just watching. Is this also not theft?
Photos on a public web page are implicitly giving you permission to view the photo and the technology need you to have a local copy for viewing. That does not mean you can grab the photos from say National Geographic and re bundle them put them on you website surrounded by adds. They are not giving you permission to do anything but view the pictures.