The article even discusses certain readers' developing relationship over time! The book hasn't changed, the text is static. Even within a person, the understanding of the text is fluid. To say it could possibly be misunderstood is to say that there is a wrong way of understanding, but clearly there are at least multiple correct - or at least not incorrect - understandings!
A certain subculture of online males have fallen in love with Patrick Bateman. Now some of them might not have read or watched American Psycho, so to say they misunderstand the art is nonsense as they haven't actually seen it. For those that have and still choose to worship the obviously awful character, I see a lot of people say they haven't "understood" the film/book. They have! They just disagree with author's own interpretation!