It rather irritates me to see frequent aggressive allegations by interested parties that copying files of 'intellectual property' is theft.
Theft means taking an item belonging to someone else. After the theft, the thief has the property and can use it; the original owner no longer has it and can't use it.
When a file is copied, no-one is deprived of the copied item. The author and any other rightful owners still retain their original copies.
The author may be deprived of a payment to which he feels entitled, but this is not a matter of theft. You can't be robbed of money you've never had.
Whether copying files is immoral is something for people to argue about. Whether it's illegal is something for politicians to argue about. I won't try to argue those larger issues here. I merely point out that 'theft' is the wrong name for it.
In practice, a large proportion of people make unauthorized copies of files, and therefore seem to believe that it's a moral thing to do, or at least not very immoral. If the propaganda floating around convinces them that 'theft' is an appropriate description of what they're doing, there is a danger that they'll come to regard other kinds of theft too as moral — or at least not very immoral. I think it would be better not to use words so inaccurately.
I also think that people who think they can stop unauthorized copying, or reduce it to a minor problem, are trying to hold back the tide. Like it or not, this is something that is not going to go away.
Personally, I still make a habit of paying for books, music, etc. Maybe that's just because I'm not young enough to be accustomed to the new way of doing things. I feel that the moral position of intellectual property owners is arguable either way, and not as clearcut as they mostly think it is. Certainly, the continuation of copyright restrictions for decades after the author's death seems to me absurd, and I don't understand how it can be justified.