It's all about whether you look at libraries as an exception to copyright which has been carved out for the public good, or whether you look at libraries as something that is naturally allowed within copyright.
Put it another way: the article argues on the basis of a library's purpose. I'm ignoring that, and merely looking at a library's right to exist. If you see the purpose coming first, and the right to exist being created on the basis of that purpose, then the argument in the article holds. If you see the right to exist coming first, and the purpose merely being why people take advantage of that right, then you get my position.
Maybe this is one of those American versus European things. It looks from my cursory examination (and I could easily be wrong, and welcome a more informed opinion from anyone who knows better) that the doctrine of first sale is an American thing, and European laws give more rights to the copyright holder.
This may be somewhat muddied by his use of "defend" everywhere, rather than something else. Anyway, I think he has a decent point, that libraries were last century's big threat to IP holders (would have liked to see some citations on the controversy though), the government decided a public good would be served with a smallish sacrifice from the industry, and that filesharing is a similar but much more efficient execution of that public service (but at perhaps too big of a cost to the IP holders.)
[1] https://en.wikipedia.org/wiki/Public_Libraries_Act_1850