As someone who grew up in the "golden age of piracy" who remembers those stupid FBI warnings on VHS tapes, I've never been able to wrap my head around that point of view. To me, it's always been propaganda that creates this so-called anti-piracy morality.
The idea that piracy is stealing is so foreign to me. Stealing/theft is a very specific behavior. Nobody called it Theft when competitors followed around Shakespeare and made copycat plays. Nobody STILL calls it theft when we see stupid copycat movies come out. Nobody called it theft if you got a "copy painting, signed by actual painter" before modern copyright law. Now they call it things (not usually quite theft).
To me, piracy just lacks all the hallmarks of stealing. Hell, I've been in lawsuits. In every other realm, the Law draws some very clear lines between real damages and potential ones, and in many cases if I have to sue somebody, the law might even PREVENT me from seeking the latter. So what's so special about piracy that so many people's headspace have this attitude the "how the world works" goes out the window and it's really stealing?
To me, it's always going to be a matter of propaganda. Very successful propaganda. And I think your last sentence backs that. The big media IP owners started pushing the bubble of "it's stealing" to libraries as well, and only backed off when it didn't work. They were somewhat more successful with "used games" and have largely succeeded in killing the used game market off in some domains. I consider it stealing if a game company locks a physical product behind a single-use code so that they can seize part or all of the product if you purchase it used.
But here's my counterpoint to all of the befuddlement. The companies don't call these things products anymore, but licenses (so they can seize them at will from people who paid for them). How can you steal something that you can't own in the first place?