Before I respond, let me be clear that I absolutely think copyright law is broken and needs significant reform -- at a minimum to make the time until something goes into public domain be only a few years (like it was in original 18th century statutes), not a century or more That said...
Sharing/copying should be encouraged as a social good. Sharing of knowledge is what made our civilization, and keeps it alive. Voluntarily allow a few elite control over what may be copied and who can copy, and you weaken civilization.
I always find these sorts of arguments hilarious. Because you know who funded the arts before copyright existed? Rich dudes.
How did one become an artist in the age before artists could make money off of publications and copying? Well, you had two choices:
(1) Be independently wealthy. A lot of art, music, literature, etc. used to be created by only those filthy rich who didn't have to work for a living. So, if you had nothing else to do and were bored, you could afford to make art.
(2) You're not rich? Well, if you want to be an artist, musician, writer, or skilled craftsman, you have to find yourself another rich dude to fund your work. In other words, you found yourself a patron, because otherwise, how are you going to support yourself?
If you actually want art that requires significant SKILL and TRAINING to learn a craft, those are your primary choices without some concept of intellectual property.
There are other ways for artists to earn a living.
Sure, you can say performing musicians have to tour rather than making money off of recordings, but what about the composers who actually write the songs? Lots of pop artists don't make their own songs -- they rely on expert songwriters to do that. How exactly does one make money off of those sorts of creations? One can't exactly become a "touring songwriter." (I mean, yeah, improvisation is fun and you can make up crappy songs on the spot for a paying audience I suppose, but there's little incentive then to spend time crafting an actual good song...)
So far, I've just been talking about pop music, but it gets harder if you want someone with real talent to devote months or even years to an extended project -- like a book, for example. And how about training? Mozart spent maybe 15 years learning the craft of composition before he began writing stuff of a "mature composer" with thorough training in how to write music. Who pays for those 15 years of training before one can even begin to compose?... and then one's compositions are just shared with no reward for the person who spent his life acquiring the skill to make them.
That's ultimately the problem with these arguments. A system without any sort of intellectual property makes it much more difficult for anyone to spend significant time on any given creative project, since no money can be made from that lost time... let alone taking any time to learn a skilled craft.
Art thus becomes only an amateur occupation, something your crappy band in a garage does improving stupid songs on a weekend, but no room for any possible types of refinement or skills. We expect doctors and engineers and scientists and programmers to spend years refining their skills so that they can produce a quality product. And when they do, they are rewarded for their work. But if you're a skilled artist who took years to learn a trade, too bad -- we still want you to make art, but we want you to donate it to us for free. Find some other way to make your money, thanks.
Unless, well, you're a rich dude and can spend the time acquiring random skills and putting time in creative tasks that won't make you any money. Or if you can find a rich dude to serve as your patron.
Yeah, once you're an established artist with a record, you might be able to get some crowd-funding or something today, but good luck to get that money to spend a year or two researching and writing your first novel, which you then generously donate to the public without any reward.
Basically, you're right -- to some extent a bunch of rich dudes control what may be copied now, and that may be restricting art. But guess what? You get rid of intellectual property, and you also risk reverting back to a system where only rich dudes fund art again.
At least in the current system, you can vote a bit with your money -- you can influence the corporations by choosing what art to buy or not to buy. In a patronage system, it's really just the elite who get to determine what art gets created, because they're the only ones with the time or money to fund it.