There's a wrinkle here, though. He talks about downloading three albums from an artist he never heard of before, and finding that he liked them. Then when he sees a fourth album on Amazon, he buys it. But he never went back and bought the three albums he had downloaded.
To me, that's where he crosses the line. I'm willing to accept the general idea that he ought to be able to preview content for free. But if he likes it, and it's for sale, he's on his honor to go back and buy what he likes.
And not just because it's the right thing to do; failing to do this is also stupid, by the author's own criteria. Look at it from the point of view of the artist: there's a customer out there who likes four of his albums but who has only paid for one. So the artist is only getting one-fourth of the economic feedback he should be getting to create more content. In other words, in his haste to make sure he doesn't reward content distributors who do things he doesn't like, this author is missing opportunities to reward content creators who do things he likes.