Through a paradigm shift, which is long overdue.
Should the public have free access to scholarly papers and pay to see the doctor, lawyer, and geneticist?
Should the public have free access to musical recordings and pay to see the artists live?
Seems to me in both cases the net effect, the consequence, would be a higher quality of public discourse and appreciation. And that would be in the public's interest.
By comparison, implicit in your argument is an endorsement of the current system, wherein 77 years of copyright is just fine. From a deontological perspective, perhaps. Certainly lawyers make their money perpetuating a purely deontological view of the world, claiming they're the only ones who can parse the ontology of duties.
This divide between the deontological position to a consequentalist position is exactly the bridge Lessig believes the Supreme Court wanted him to cross, and he failed to realize it. Free Culture was his mea culpa.
I'm not sure how old you are, but my personal observation at 35 is that the quality of public discourse has improved since the advent of the internet. It would be a tough sell to claim that more information is better, but more access to high quality information is worse. Fundamentally, it's not about honoring the terms of scams corporate lobbyists perpetrated as we awoke from a 50-year TV-induced coma. It's about the public interest. In that paradigm, a consequentalist paradigm focused on the public interest, more access to high quality information is better.
Building the quantitative body of evidence to examine the consequentalist position is exactly what scholars have been laboring at for the last decade. And arguably the most advanced, sophisticated, educated society on the planet has examined the evidence and found it sufficient to directly, explicitly, reject in whole and in part, the deontological arguments of the old business model.
I will stretch this a bit further: if you look at history, I think you will find progress is often a story that starts with a deontology, a consequentalist argument forms, which is then backed up with evidence, adopted, and then forms the foundation of a new, hopefully less misguided deontology. If you can identify a deontology, look for consequentalist arguments that oppose it.
edit in reply to geoffschmidt: How to implement? I think we have seen that grandfathering current stakeholders has historically been an effective path to progress in the long term. As the new rules apply to more people, the old rules enjoy progressively fewer supporters, and eventually the new rules prevail. In terms of defining their copyright as "property", we're getting into the merits of the term "intellectual property", which is a red herring. There is no such thing under the law, but it is a very useful conflation of ideas for patent lawyers who need to pay off their Maseratis. The facts will set you free.