You want to redirect the conversation to the question "why do copyright owners insist on describing copyright as a property right, rather than say as a regulatory privilege or a tort?" Fair enough. If I took a bit more time for research, I could probably come up with a very sophisticated answer, digging up 18th Century texts to support my position. But instead I'll give you a much simpler one, one that might not satisfy the philosophers, historians, and economists among your readers, but one that happens to be accurate (and will probably work for most lawyers): Because pretty much everyone refers to copyright as a form of property. Contrary to the premise of your post, it's not just "copyright owners" who use the term "property" in this context; it's exceedingly common for those on all points of the copyright spectrum.
At law school, I took "Introduction to Intellectual Property" (my emphasis) from EFF Advisory Board member Mark Lemley -- hardly a shill for the labels and studios (but an excellent teacher, by the way). When academics who support narrower and less robust copyright laws file amicus briefs, they call themselves "intellectual property" professors. Examples here and here. Hell, the official EFF bio for Fred von Lohmann, one of the nation's most prominent warriors against Big Content, describes him as "specializing in intellectual property matters." If they can all live with describing copyright as a form of property, why can't the rest of us? Are they all "prejudg[ing] the outcome" of copyright issues because they -- just like their counterparts on the other side of the copyright aisle -- use the term "property"?
Maybe I've just spent too much time in simple-minded fields (litigation, politics, journalism), but I just have a hard time getting too worked up about what label we attach to copyright. And I suspect most non-philosophers agree. Consider this thought experiment: Go to a studio head and say, "I've got a deal for you. I'll give you your copyright wish list: repeal first sale, make Justice Ginsburg's concurrence in Grokster the controlling opinion, delete Cablevision, Perfect 10 v. Amazon (and a few other Perfect 10 cases while we're at it) from the law books, and codify a "making available" right. But here's the catch: From now on, you are forever forbidden from referring to copyright as 'property,' and must instead call it a 'set of social relationships.'" Or go to a copyright skeptic, and say, "I've got a deal for you. I'll give you your copyright wish list: reduce the term of copyright back to 14 years, expand fair use, eliminate the derivative works right, and repeal the anti-circumvention provisions of the DMCA. But there's the catch: From now on, you must refer to copyright as property; no more of this 'set of social relationships' mumbo-jumbo." I'm confident both the studio head and the copyright skeptic would take those deals in a heartbeat. Ultimately, it's the substance, not the label, that matters.
It's also my (admittedly anecdotal) sense that the dominant theme of copyright owners' arguments these days in pressing for stronger anti-piracy enforcement is not so much about "property." Rather, it's about "jobs." In this summer's Jammie Thomas-Rasset and Joel Tenenbaum trials, the plaintiffs' attorneys and witnesses focused on layoffs at the labels, blame for which they laid at the feet of illegal peer-to-peer users. And this 2006 MPAA press release is typical: "MOTION PICTURE PIRACY COSTS U.S. ECONOMY THOUSANDS OF JOBS, BILLIONS IN LOST WAGES." Perhaps copyright owners have concluded that arguing to the courts and politicians, "Hey, it's our property, and no one should be allowed to steal it," is not as effective as contending that copyright infringement puts hard-working Americans -- especially the non-wealthy recording studio engineers and session musicians invoked by the labels at the Thomas-Rasset and Tenenbaum trials -- out of work.
Lastly, I want to respond to your criticism of the media executives you quote making broad claims of ownership in copyright. I guess I'm a bit puzzled by anyone's surprise that big copyright owners would take strong stands -- both substantively and rhetorically -- in favor of copyright. I don't think I'm revealing any big secret by saying that entertainment executives do not wake up in the morning and ask themselves, "What can I do today to promote a view of copyright that properly balances the need to provide incentives to 'promote the progress of science and the useful arts,' with a robust public domain and the right of others to remix and reuse the works that we have created?" Rather, they say, "What can I do to make my company a profit?" Why should we expect them to act any differently? As one wag said:
By pursuing his own interest he frequently promotes that of the society more effectually than when he really intends to promote it. I have never known much good done by those who affected to trade for the public good. It is an affectation, indeed, not very common among merchants, and very few words need be employed in dissuading them from it.
I knew I couldn't get out of here without quoting at least one 18th Century text...
