It is, of course, terribly silly to pretend that a given entry in a TV series, movie franchise, comic book run, or whatnot never happened. Why, even I refuse to do it any more, and I’m a nutjob.
That said … there are still things we simply refuse to talk about. Yes, we admit that Chuck Austen wrote that X-Men run with Nightcrawler being a pawn in a plan to destroy the Catholic Church with magical communion wafers; we simply do not talk about it here so as not to give anyone an anger stroke. For similar reasons, we do not allow conversations about the novels Hannibal or Hannibal Rising because there are children present and it is not necessary to scar them needlessly; and it is likewise not necessary to go into any detail about the post-Sin City work of Frank Miller because it makes people cry.
Anything else?