Oh, I think I see it now... you don't think this case has to do with intellectual property?
It doesn't. This case is about the right of the producer of a good to set arbitrary restrictions on where his product ends up; in this case, regional editions of textbooks. If first sale holds true, then the producer has no control over his products after the first sale; if it doesn't, a producer has the right to restrict the flow of his wares from one arbitrarily defined area to another.
The whole reason the "let's get rid of first sale" idea sounds so absurd is because we're missing their side of the picture. They're trying to force people to buy directly from the publisher. "First sale" is just collateral damage.
They're trying to force people to buy their products only via channels approved by the producer. This means cutting off a whole lot of the disintermediating factors the Internet provides; the customer's ability to make sound economic choices by comparing offers from different vendors would be impeded. The producers in this case want the right to create regional monopolies, essentially. And we all know how good monopolies are for business.
Edit: They're trying to make the argument that the person buying second-hand "had no right to the product".
The argument they're making is that the reseller had no right to resell the goods he obtained in one region to people in another, thereby severely undercutting the producer's set prices for the region.
In the end, I think this will hinge on the whole "Licensing vs Ownership" thing that the producers of copyrighted goods have been on about for some time now. If you only buy a single, non-transferable license to a product, then reselling it is definitely forbidden; if you actually buy a single instance of a product with a full transfer of ownership rights from the producer to you, then reselling is definitely OK.