Arguments that it is stealing are also nothing more than rationalizations. That's what both sides wield: it's a war of rationalizations.
(I tend to be more convinced by the "it's not stealing" rationalizations myself, simply because stealing an object makes it unavailable. If someone stole my bicycle, I'd be upset. If they cloned it in a Star-Trek-style "replicator" and took the copy, I couldn't care less. If you lend a book or DVD or SD card or whatever to someone, upon it being returned, you have no way to test the hypothesis "a copy of this was retained by the borrower". Not testable is not real, for all practical purposes.)