When reading "The Miller's Prologue and Tale," "The Franklin's Prologue and Tale," and "The Nun's Priest's Prologue, Tale, and Epilogue," from Chaucer's Canterbury Tales, I could definitely see why the tales might be banned. The characters described in the tales have glaring flaws, but so do the tale tellers themselves. I think that the idea of humans being innately flawed, however truthful this notion may be, makes people in general feel uncomfortable. It forces them to consider their own flaws, which is typically a discomfort they'd like to glaze over or ignore. This, in my opinion, is a possible reason as to why the tales were banned that would not have been fomrally stated.
Consider the Miller's tale first. The flaws that are brought to the surface include lust, lying, and insensitivity. The lust is between Nicholas and Alisoun, who disrespect Alisoun's husband to indulge in their sexual fantasies of one another. Many people can most likely identify with this feeling of lust, but would be uncomfortable to admit it--especially in a society dominated by Christian ideals. Similarly, the lying comes into play when Nicholas tricks Alisoun's husband in order to sleep with her. We, as humans, have all lied in our lifetimes, but see it as something to be embarassed about. That would be another element of discomfort that might motivate people to ban The Canterbury Tales. Finally, the insensitivity is seen when Nicholas and Alisoun rudely toy with Absolon. This is something a reader might relate to from childhood, humiliating someone who is in a vulnerable position, and resenting it in hindsight. For me, personally, these are the kinds of things that make me feel uncomfortable.
When thinking of The Franklin's tale, new flaws are represented in Dorigen, who secures a new lover in fear her husband will not return safely from England. She shows the flaw present in many humans, who act in a disloyal manor in order to avoid being alone. Understanding and realizing this flaw is difficult for those struggle with it, because they don't want to take the necessary means to change it...for that would mean being alone, the one thing they truly. Thinking of these kinds of things makes it uncomfortable for the reader if he or she can relate to Dorigen, but also--the sexual explicitness of this tale would make most uncomfortable. I can see why the Franklin's tale would be banned, as well, even though it does have a happy ending.
Although the Nun's Priest's Tale is about animals, the flaws of pride are still very relateable to humans. The effect of having too much confidence, we see in Chanticleer, who is taken advantage of by the sweet-talking fox. For most people, thinking of how easy it is to be tricked by an astute rhetorician might make them feel rather uncomfortable, especially in the time which The Canterbury Tales were written. Being forced to come to terms with the negative effects of being too egotistical is something we might not want to face.
In general, The Canterbury Tales are a little bit distressing to read--perhaps I feel this way doubly as much because of how difficult it was to read old time English, but even if it were written in modern parlance, I would still feel uncomfortable reading them. Their message is to expose the flaws in humanity through the story-tellers, but also through the happenings in the stories themselves. I think that the way they shed such a negative light on human character makes a reader feel uncomfortable, even if he or she is considering that The Canterbury Tales are meant to be a satire. No one really likes to think about what is wrong with themselves or those around them--perhaps that's why The Canterbury Tales were banned.