Readers' Perspective Book Club discussion

I enjoyed "Divergent" and am glad I read it. I can see a great story in the book. I found it hard to get into, but the more I read, the more I got on board with it all.
However, I still found it very hard to suspend my disbelief of the entire concept behind the factions. Maybe if I read the rest of the series, it will give me answers that will set my doubts aside.
In terms of the first book, though, I had a very hard time accepting the overwhelming predisposition the majority of people had for their factions. Doesn't this go against what we learned from "The Breakfast Club"? (Clearly, I'm calling on my very scientific sources for this discussion haha)
I love fantasy, sci-fi, and comic books, but I couldn't get my brain to latch on to the faction thing. Good thing the story was entertaining enough to keep me reading.
Anyone else have thoughts on this?