First off, I’ve sat in many book stores and read magazines and books and never once had anybody kick me out or object.
Second, do you really think that all the people walking past a stadium where a paid concert is happening are thieves because they hear the music from the outside?
Third, they aren’t “losing money.” They’re just not making money. Its theoretical money, it doesn’t exist. If I told you I’m selling my old smelly socks for $10,000 and you refuse to buy them, I didn’t lose any money at all. You didn’t steal $10,000 from me by not buying what I wanted you to buy.
Is it “stealing” if you read a book and then tell your friend all about it and they don’t buy the book because they don’t think the story sounds compelling? Is it “stealing” if you buy a book and then let your friend read it without buying their own copy? What if you buy a book, read it, and go online on your blog and give the book a bad review, and hundreds of people that read your review now don’t go and buy that book? Did you “steal” all those potential sales from the author by giving your honest opinion on their book?