The act of transmitting a digital file does not directly cause harm to anyone, but by creating a demand for it, you are in turn driving an industry that violates the rights of people in order to keep supplying it.

We already know that people are killed in order to feed the black market for transplantable organs, so why would we allow an industry with all of the same risks to exist purely for the sake of art?

I think you may be making a logical error here. Wanting or needing a transplant, or buying sneakers, or any other consumer product for which there is a legitimate and legal supply chain, does not make you responsible for any parallel illegal/unethical/immoral supply chain. There are black market supply chains for everything from food and basic necessities to luxury goods. There is no fool-proof way to ensure that ANY product you purchase didn’t derive at least partially from an immoral supply chain. It is impossible to track all products that closely. The fault is not with the consumer but rather with the immoral supply chain participants. Don’t take away the agency of those who participate in such things.