But the point of the original article is that "just rent it again" is entirely dependent on the renting authority deciding they still want to rent it to you. If Kindle decided (or was pressured) to censor a book for whatever reason, then it has enormous ability to dictate exactly what type of information you're able to consume.
This assumes anti-competitive authorities as monopolies but that is as far from reality as can be expressed.
Amazon Kindle doesn't own the content of the books to be able to censure them, they can't legally censor or edit books that weren't censored or edited by the writer/publisher.
Also, there are dozens of ebook stores - a vast competitive market to choose from - not to mention many libraries have ebooks and print books available and interlibrary loans are awesome to get things you want even if not available locally.
That's only true if Kindle has monopoly power over books as a whole, which is obviously not the case.
Now, services like Kindle or Steam deciding to revoke access to prior purchases is a potential Big Problem...but as of yet, it remains just that: potential. And at least in theory, there are government agencies that are charged with protecting against abusive behavior towards consumers (obviously actual results there are somewhat mixed).
Well, the whole point of the article is to observe a trend. None of this is a big problem right now.
But economic incentives might push the renting model to become the main - or even only - model to use many goods and services in the future. Similarly, trends about the number of service providers seem to point towards consolidation as well.
So if those trends hold true, we might at some point have Megacorp Inc. offering Living-As-A-Service. And then we would have a problem.
