Oh, I kid. It's not because they're straight. It's because they're John Winchester's sons, and look at what a gigantic fucking tool that guy was. "I am going to impart a piece of vital and deeply disturbing information in a whispery voice right before I die!" Drop dead, asshole. Erm. I mean, drop dead some more.
ANY-way, where was I? Oh, yeah. The pointless internecine douchebaggery. Sam's picking at Dean because he's certain Dean's shutting down like he always did in the past and not dealing with their father's death at all, which is A Very Bad Thing. Dean's furious with Sam for picking at him, and what's more, Sam's sudden bout of posthumous obedience to their father is chapping Dean's ass, because when their father was alive, Sam went out of his way to be contrary, and all this crap coming out now amounts to too little, too late. Did I touch on all of the major points? Don't worry if I missed a couple. After all, we'll be dealing with them for the rest of the season. Fight over and splendid day thus ruined, Sam runs into the bushes to cry. I mean, "to call Ellen." Dean sets his jaw manfully.