The words “piracy” and “theft” are being used by copyright holders as deragatory terms for copyright infringement. Of course, they are used wrongly, misappropriated from other contexts to evoke emotions that the sterile correct terms, such as “copyright infringement” or “unauthorized copying” do not.
However, there is one condition in which the term “theft” actually applies. Interestingly, it is not what Disney et al would like it to be. But first, a definition or two:
A person is guilty of theft, if he dishonestly appropriates property belonging to another with the intention of permanently depriving the other of it
Obviously, this does not apply to copyright infringement, because the “depriving the other of it” part does not apply. However, it does apply very much to something very similar, namely the theft of copyrightable content from the public domain.
Copyrights expire, and after expiration, the content formerly protected becomes part of the public domain. Copyright holders regularily appropriate this property of the public by creating new works based on it, or sometimes wholesale lifted from it. Disney is famous for taking fairy tales as the source of their kids movies, for example. It is legal for them to do so because copyrights expire (something they hate when it comes to Mickey Mouse). However, if they appropriate this intellectual property of the public in such a way as to deprive the public of it, as it happens if everyone else who wants to make a derivative work has to fear a lawsuit, then all but the word “permanently” applies.
Unfortunately, the commons, the properties of the public, are not guarded anymore. Our politicians have sold us out and we don’t protect them well, either. Damaging the public good is punished far less harshly – if at all – compared to damaging some private property.