Indeed, his whole speech was in defence of libraries and of fiction... Actually, I think, in a broader scope it was defending people's possibilities to imagine. You could (partly) do that with (moving) pictures and theatre as well but he laid emphasis on written material - both the writer and the reader side of it. I think that's a justified emphasis because written material leaves more to the imagination and there is more of it.
One of the most basic ways to be able to fulfil that, people's possibilities to imagine, is through physical libraries. If everyone was born with a (mobile) internet connection, free of censorship, small enough in cost that it is affordable even in hard times and of liberal capability, a virtual form of libraries might be able to take over (some combination of e-reader, wikipedia and specialized chat system inhabited by the readers and 'virtual' librarians might do the job). Do remember, currently, young people first need to have some capability to navigate the internet, learn to handle a device capable of acting as an e-reader and learn some things about e-books and how to get them on their device before they can start reading them. Compare that to libraries for which they only need some push to actually pass that 'scary' librarian at his/her desk and their own two feet to walk to the library in the first place. Also, while there are still people in developed nations (not to mention the nations that are still developing) that have no easy access to internet, physical libraries have a very substantial role to play.
I read Mr. Gaimans (edited) lecture on the website of 'the guardian' from the link in the article. It made me remember all the emotions and wonder I felt while reading through all those fantasy and science stories I have... and the times I (try to) put something on paper as well (try to, because there are too many things I am interested in, including reading and therefore I mostly lack the time. Maybe that will change one day. The day I will stop imagining probably is the day I stop living).
I didn't hang out a lot in libraries as a child... but I did every now and then... and always loved the stories I read. At the end of (equivalent) high-school I still had a few reservations about reading due to the mandatory reading lists I had for the foreign languages I chose as subject (English and German. My native language is Dutch). But it didn't withhold me from also finding pleasure in reading. Also in much of the literature I had to read for those language subjects. It was at my early twenties that my interest in fantasy reading really took off and at that age I had enough income (savings form a Saturday job in earlier years, then student, then regular jobs) to buy the books I wanted to read, second hand and I had the internet to search for reviews and interesting authors. Still I buy most of the stories I read in physical book form. I find that form of reading superior for all situations except when mobile and weight-restricted. I do have a smart phone and I do have a very capable tablet. I'm very familiar with computers and the internet... still I find, for stories, hard copy a joy to read above all others.
Of course this is very much my own opinion and I do think everyone is entitled their own. When reading the lecture, however, I found myself both logically and emotionally agreeing with it and I hope more people will.
For it is the politicians mostly concerned with making the decision to do so, my opinion is that a policy involving the closure of public libraries is one of the worst things a politician could do apart from outright lying or doing something criminal.