The lecture about incest was indeed boring and I didn't really understand why it is in this particular version as there seems to be no interaction between those two so far, but the funny part is that, when you think about it, those people portayed as shining examples in the lecture, you know, ordinary folks who fall in love with each other and just happen to be siblings, they are the very reason anti-incest laws exist in the first place.
THESE are the true villains, not "perverts" for which this is but a kink, nothing but a fantasy to get their juices flowing. It's not the fantasizing those laws ought to prevent, its the execution - the exact thing the folks idealized as heroes in the lecture happen to engage in.
Oh, the sweet irony.