Maybe it's the combination of recently watching Olivia-era Cosby Show, playing The Force Unleashed on PS3, and reading that interview with Fanboys director Kyle Newman, but I think I've cooked up an understandable metaphorical situation with Star Wars fans. Take the tone of the storyline of The Force Unleashed and compare it with the tone found in Episodes I, II, and III, plus take into consideration what Kyle Newman says about the Saga itself, and consider the fact that Olivia was a step-child.
Imagine this: growing up, you and your two siblings get along pretty well. Together you do things that define your childhood and adolescence. Well, unfortunately, right as you're making the transition from teenager to adult, your parents decide to divorce. A couple years later, your parents choose to remarry people that already have children from a previous marriage or they choose to bear new children with their new respective spouses. For you and the siblings you grew up with, now you have more siblings that are considered family. Growing up, you thought about having other siblings, and might have wished for more. Now you have them.
Where I'm going with this is, the prequels were, for a lot of people my age, like those new siblings. Not everybody hates prequels or new siblings, but you definitely hear from the ones that do. You grew up with the family that you knew, and now you're forced to accept a newer family dynamic. No wonder so many people went so far as saying their childhoods were robbed.