My argument was simply that not all unauthorized and/or potentially harmful misuse of others' property is equivalent to theft.
Hardly any of it ever is, which is why they're not considered the same crime (terrible scare-tactic PSAs and "WOULD YOU STEAL A CAR??" aside).
When you steal it, the issue is not in fact the stealing of the music/game/book/ect you are stealing the profits they would have made if you had purchased it.
There is never any guarantee that someone who pirates something would have bought it. There is also no guarantee that they
won't legitimately buy it at some future date.
Let's face it, most of us have pirated
something we would never have bought ourselves, and probably very many of us have bought music or a movie after illicitly experiencing them somehow. Personally, I can think of many things I've pirated but would never in my life buy, pirated
then bought, or hell, even bought and later pirated, in rare cases... in addition to things I bought without ever pirating them to begin with.
Simply put, you cannot assume that someone who has downloaded a movie, game, album, or anything else, would have actually bought it legitimately, nor can you assume they never will, nor can you assume the price at which they would.
I mean, let's say I download an album: How much financial loss does the company incur due to that? It is completely impossible to say. It's possible that I'll eventually buy it for three dollars from a reseller, or ten dollars on sale, twenty dollars at a retail store, or all the tracks individually for some other price on iTunes. It's also possible that I'll never buy it. It's also possible that I will buy it, but
never would have bought it if I hadn't pirated it and listened to it first. There are indeed many cases where pirating something has resulted in people, myself included, giving
more money to the distributor, because of the ability to pirate something and check it out first to determine if we like it.
I'm not arguing in favor of piracy from some ethical standpoint, but you simply cannot conflate copyright infringement and "theft", and there is absolutely no way to determine how much loss, if any, a distributor will incur due to someone pirating their product.