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Why did the camera, props, lighting and other workers contribute to the movie, if they weren't getting paid? How could they afford to?
In reality, of course, only the movie companies, some writers and a few big stars rely on percentages - the rest work for wages or get up-front money.
So your argument comes down to the special case where A puts out a recorded work, counting on royalties to pay for it, then B makes unauthorized copies - then A suffers, in some sense, a loss of the hypothetical revenue.
But wait, did B agree to pay? If there was no contract between A and B, then the supposed moral/ethical case for making B pay is reduced to "because the legislators said so". And if tomorrow the legislators grant a private monopoly on air to Monsanto, then by your reasoning we all suddenly become thieves.
There is a natural-rights case for copyright, but it extends only to the actual creators, and covers basically only correct attribution (as per some European laws [1]).