I'm guessing that the language is a product of the polarized positions on copyright infringement, rather than copyright infringement being a product of the language used.

There seems to be a tendency for content producers (authors, publishers, etc.) to use words like 'intellectual property', 'piracy', and 'theft' to describe the actions of others. None of those terms are terribly accurate, but they tend to use them because copyright infringement represents a potential loss of revenue to them. On the other hand, you have copyright infringers describing their actions as 'file sharing' and 'fair use'. Neither term are entirely accurate either, but they benefit from copyright infringement so they use more positive terms to describe their actions.