HBO is being smart
They are removing it for the time being and they state that when they bring it back they will do so with added content and context about how the film perpetrates many racial prejudices that were pervasive back when it was released and still around in some aspects today. HBO is not preventing people from watching the movie, it is simply adding much needed context that will hopefully strip away some of the romanticism towards the period of time the movie reflects and its writer tries to depict. Smart move. If there is a market for this film in the future, it will likely be from younger movie buffs who want to see how this film compares to many other films that contrast GWTW flattering image of Slavery and the Antebellum South, to more accurate, historical films - like 12 Years a Slave.