Well, I personally find it strange.
Although I do not directly pirate things myself, I have no idea about my music collection. Most of it is stuff friends have given me, you get the idea. I, personally, have nothing wrong with this. Humans share everything, from books to games to music (Primarily in my experience, Music).
I consider TPB to simply be an extension of the essential human urge to share things, from pirated games to music that at some point, many years ago, some bloke bought. In some cases it is only through sharing that these things still exist and, in some cases (Despite money) things are impossible to find bar through sharing.
So... With regards to music and books, I see nothing wrong with "Piracy". My love of Terry Pratchet was fueled by my school library and my friends (And my parents friends) having incredibly large Pratchett collections. I went to my first gig cause I was shown Frank Turners music on Youtube, my second gig because I was shown Reel Big Fish on youtube, my third gig cause I played Guitar Hero (Through the Fire and Flames was fucking awesome live, although one of the supporting bands outdid them massively.)
My essential point here is that with regards to music there should be no guilt. Musicians make most of their money through gigs and syndication in games/movies and whatnot, not through people physically buying their CD's. As for books and audiobooks, I apply the same logic. With regards to Non-Fiction, knowledge should be free. Information should be shared to the maximum amount of people. Without one of my fellow students downloading a library of psychology books, most of us would have failed the course we were doing (The college library was a pile of crap and the books on the USB came in at roughly 15,000 pounds. Cambridge University Press overcharges people to the nth degree). As for fiction, well, there is less of a market in pirated fiction on the internet cause it is a luxury that comes in so much cheaper.
I guess I am trying to say that in my eyes there is nothing, morally, wrong with sharing music or books. It is something everyone does. I will state that I am a socialist though, I think my political affiliation does affect my moral compass.