It's a smart move by the entertainment industry to try to rebrand piracy as theft, as the public at large understand theft as a bad thing. Legally though I think it's 'copyright infringement' which sounds a lot less sexy.
Certainly in the UK theft is "taking possession with intent to permanently deny the owner of it". Copyright infringement is not theft by that definition.
Saw this great stand-up skit by someone who was asked to compare copyright infringement to stealing a car...
It like stealing a car but
You just stick you finger out, touch the car, and it's your car!
We've often seen the naritive of Big company stealing ideas etc from smaller companies.
So stealing can extend beyond simple physical property, and could acceptably encompass IP as well.