I never said that not giving someone money inflicts harm -- *unless you would have otherwise done so*. Let me also quote myself "Without a doubt, a percentage of people who pirate a product would have purchased it if the "free" option weren't available". I agree the economic impact to the owner is zero when someone who pirates something would otherwise not have bought it. However, this just isn't the case. In many cases, the pirate would have purchased the item they took for no cost. You cannot argue (sanely) that this isn't true and does not represent a true loss to the property owner.
Reaching further, you could argue that even if they didn't want what they pirated, they would have bought something else instead; however, because they received substitute entertainment at no cost they don't need to purchase their preferred product. In this more extreme case, it's not the person whose craft is pirated who suffers, but someone else entirely. For example, if I pirate enough movies or music that I have enough content to keep me busy, it's far less likely I'll go out and buy the movie/CD I wanted but wasn't able to find for "free". Conversely, if I can't pirate anything, odds are that sooner or later I'm going to pay for something rather than live in silence.