Yes, there might be other variables affecting it too, but a blanket statement of "Piracy doesn't reduce sales" when it's primarily studied in the higher volume form of video game sales which are often pirated immediately after release and thus the effect is not clearly visible is not a good argument either.
I feel blanket statements are generally not a good fit for serious discussions. We have to keep asking the questions that will guide us closer to better data.
I can't imagine the only good studies being on games. I'm sure similar studies for other forms of entertainment/art exist too. Games are also harder to pirate, and has its own problems that are virtually non-existent for books.
And if we were to go down that route, we can further divide the affected people into publishers, authors, book stores etc. and only then can we figure out how the moral compass of each of us is really adjusted :)
Big movie studios/publishers making billions of dollars? Hard to feel sorry for them.
Indie authors/studios? I definitely have a soft spot for them.
