Well, not exactly; you're comparing apples and oranges because the original Mona Lisa has value inherent to it being the original, which the copy does not retain. But say you show up and exact copy the Mona Lisa and then take your copy home, that's not only not theft, it's perfectly legal. People take photographs of it all the time.
In software there's no difference between a master copy and the one you've downloaded, there is no additional value inherent to being the "original file" so this comparison doesn't really work.
If you can't tell the Mona Lisa isnt real because its a perfect copy then there is no value lost. The one thats on display in the museum is very likely not the real one, and yet people still feel all of the feelings of seeing an original.
If noone knew I made the copy and swapped it, noone would ever be harmed by it, right?
Well, then you'd be incorrect. Have you been paying attention at all? Even your own argument illustrates why this is. Think about why theft is illegal and it should be immediately apparent why they are different.
You have a cow, I take the cow from you, you starve and die and I make money. That's theft.
You have a cow, I create a perfect copy of that cow and take it home, we both get milk and beef, we both survive in our post-scarcity Star Trek like utopia. The fundamental definition of theft, the taking away of something that belongs to someone else, is impossible here.
If you steal a piece of art that devalues that art for everyone, which then deprives the producers of the art of income, they then starve, and I get to have a bit of fun that I could have gotten elsewhere for free, real free.
Look, the point here isn't that piracy is some magical guilt-free action that gets everyone free stuff for no downside. I'm not arguing that it should be legal. I'm not arguing that it's moral. But it is a fundamentally different crime than theft. We've been talking in circles about this for two days and it's pretty clear that neither of us is going to move off our opinions on the matter. Agree to disagree, then?
I actually didnt know how you felt about it until this last post, and I mostly agree. Ive been seeing an aversion here from people to acknowledge the downsides of it though and thats been frustrating. And I even pirate stuff myself.