Sam doesn’t bat an eye at the manhandling, maybe even slightly leans into Dean, focused on the screen and paying the rest no mind, especially

with Bobby standing there, grappling with whether to call it out or not, watches them intertwined in his living room. it‘s another of Sam and Dean‘s many too-close habits, and he knows they don’t mean anything by it. it’s just…a bit unsettling to watch.

And they discuss the major aspects of it in class, and of course also the topic of incest.

First it's strictly related to the book and it's characters, but then it turns into this full blown discussion of the general immorality of incest.

the students are loudly discussing on how wrong and sick it is.

And Sammy just sits there, feeling caught and guilty and ashamed but also angry and defensive.

hearing all that and thinking 'I'm sick. These people would think I'm sick for what I have with Dean if the knew. That it's wrong. But they have no idea. They don't know us. just don't understand"

and maybe the professor asks for his opinion on this topic and Sam just stutters out a response, or just grabbing his back and storming out, leaving everyone confused.

Dean: Oh thank Fuck. I knew I wasn't gay.

Sam: what..???