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?