I can imagine reading an rms essay on how coming into my yard and taking my ladder without permission, using it without damage, and returning it before I noticed it missing imposed no harm upon me, so the taking of my property was not wrong, though the ongoing possession would be.

To your later-added devil’s advocate paragraph: rms is fine with you selling a product that includes GPL code and as far as I can tell always has been. What he’s not fine with is you imposing restrictions that prevent someone that you do sell the code to from effectively modifying or further sharing that product.

Nothing in the license precludes the sale of such a combined work though, as in your devil’s advocate query.

I’m not even sure where the confusion or disagreement is in this sub-thread to be honest. The license is short and fairly clear; there’s ample additional “what does this mean for inclusion of GPL code in commercial products?” FAQs and a fairly large body of commercial products openly marketed which include GPL code in them.

[0] - https://www.gnu.org/licenses/gpl-faq.html#GPLCommercially

In your scenario, the user won't have access to the code they'd need to modify the product you sold them. That is the harm the GPL is designed to protect against.