However, this isn't just gratuitous. Here the issue is similar with the sci-hub one: there's a fairly legitimate motivation for piracy, so there's a lot of comments over "free knowledge so copyright is theft", and a bit of "piracy is theft". But not all piracy is equal, and sharing knowledge (research papers, etc) is useful and participate into making people more informed, but the bulk of piracy is part of the problem.
1) It's diverting considerable effort that could go into free software. If you had to either pay for Photoshop or use a free solution, Gimp and Krita would get insanely more resources. In other words, piracy is a key element in closed-software dominance.
2) Popular movies and TV shows are made to keep people as uneducated imbeciles. So sharing research papers is not the same thing as what commonly falls under the "piracy" moniker.
That's what that snark meant.