It seems to me that there are three different arguments going on here.

First: from a legal perspective, the work itself is considered a service, and the illegal copying/consuming of that work is legally considered "theft of services." You may not like this definition, but it is the law of the land (for some values of "land" including the US of A.)

Second, there is the economic argument. Here, you are claiming that "scarcity of resources constitutes the core of Economics." This may (or may not) be the case, but the notion of intellectual property currently has a place firmly within the domain of economics, even if not at its core. Again, you may wish it weren't, but intellectual property is a mainstream economic notion.

Finally, there is the moral argument, which seems to be that "copying should be permitted, since it does not take anything corporeal away from anybody." In this case, I think the case of JRR Tolkien is instructive; you may recall that a US publisher, Ace paperbacks, printed and sold copies of "The Lord of the Rings" when another publisher (Ballantine) actually had the rights. The Ballantine edition contained a plea from Tolkien stating that "Those who approve of courtesy (at least) to living authors will purchase it and no other."

Morally, I am with Tolkien on this one. I think that common courtesy (at least) requires that the people responsible for creating a work of art be remunerated for that work by those wishing to partake of it, if they so desire.

These are good arguments. I'm not aware of theft-of-service laws being used against copyright infringement, possibly because copyright laws are more obviously applicable and call for vastly higher damages. Indeed it's the draconian nature of current copyright laws, and the intrusive tactics needed to successfully enforce them, that make me cautious about using analogies to theft rather than the specific tradeoffs of having copyright laws when we decide where the line should be drawn.