well, if we had a post-scarcity economy, but we don't. We are in transition. That means the people who produce the most valuable products -- information -- need to be compensated until we can get to a point where people don't need money to buy things.
The point I illustrated with the money counterfeiting example, is that copying things cannot be said to be "harmless" . In the case of money, it is a standard of exchange that lets us have economic relationships between ourselves over time. It allows us to store value, and use it later as well. Allowing people to "cheat" that system undermines it for all of us. How would you feel if suddenly your life's savings were worthless because millions of people started copying money and inflated it to nothing? Money is like traffic lights. If we all mostly obey them, it benefits all of us. If a significant fraction ignore them, we are in trouble. Most of society's rules are like this: our stability depends on most people not being disobedient.
With respect to other forms of information, you can have the same effect. If it takes me 18 months, and $5 million to pay a team of 40 people to work on the next video game (say, Half Life 2), because these programmers have lives, car loans, mortgages, children, and other things they are responsible for, then I need to sell 100,000 copies of this software to make back the money I used to pay the programmers. If 50,000 people pirate, then I need to sell the remaining 50,000 copies at $100. If 75% of the people pirate, I need to sell for $200. What's that look like? Inflation.
Of course, this won't happen because people are sensitive to price, and less people will buy Half-Life2 for $200, for example.
The problem with the band theory is that painters and bands are 1-5 people, operating on somewhat chaotic schedules. In order to get a larger group of people to work together, say, 30 people, over an extended period of time (say, 2 years), you need to shelter them from risk, and that means paying them up front while developing. But the person who supplies this money (i.e. the capitalist) won't do it if he can't get a return on his investment.
The result is a reduction in goods produced by larger groups of people.
Now, I love individual art and bands myself, but I have seen awesome things that a large group of dedicated humans can do over 2+ years if they are managed and kept together effectively (Lord of the Rings trilogy for example). I'd hate to lose that form of art, just because some immoral people can't understand that they can harm people, even if they can't see it.
The alternative is government *FORCING* you to pay artists, by taxing everyone, and paying artists to produce things. You're going to pay, even if it means the government has to subsidize movie studies and game companies. Isn't it better to have a free society and choice, rather than have the government take that choice away from you and force you to pay for art you don't like?