People ban influences they don't like, like how Christian parents did with metal, rock and roll, etc. Literature has always fallen in the same traps, don't read Camus or Sartre because they're communist, you can't read Machiavelli because he's a pragmatist and that's evil, you can't read Nietzsche because it's just the raving of a man with syphilis, don't you dare read Ovid because he is a lecherous traitor to our glorious Augustus and defiles the sanctity of love, and so forth until most great authors are on the list.

Censorship is what everyone in power wants. It has something to do with the subversive power of literature, but also if a work doesn't fall in line with the contemporary thinking, even in terms of something as straight forward as Sidereus Nuncius, those on top will try their hardest to eradicate and suppress it, but rarely with lasting success. Great books are humanity's property, and can never really be withheld from us. They will find their way to our eyes.

Good post, it brings up some of the most important questions of writing.