I find that most HN contributors are well-off, don't make too many movies/songs and contribute under their real name. Put those facts together and you can easily get a hivemind reaction of "piracy is extremely evil with zero justification ever for anyone".
1. "I wasn't going to buy it anyway so the author isn't losing a sale"
2. Zero incremental cost!
3. "If I like it I'll eventually maybe buy it" (if only I could use that defense after stealing a Porsche)
4. Paul Graham's oddball (in my opinion at least) "stealing the smells" re-imagining of property. [http://www.paulgraham.com/property.html]
I think whether HN is pro piracy depends very much on which comment thread you look at: If "DRM" is part of the title, the mood will be very different from "Show HN: My New Book", in my experience...
A lot of people do all these things- I thought that was relatively well known. Not that I am condoning it, but if we're talking about drawing the line... it's very far away from where you're discussing it. I suspect it lies somewhere near "is a real physical item".