Now, I want to look at an earlier conversation in the episode: The conversation where Sam tells Dean how much he hated being left at PPMM as a child. Dean deflects by telling Sam that PPMM is supposed to be fun for kids: "It's not like I left you in jail." But Sam continues asserting that him being left there was neglectful (not Dean's fault, as Dean was just a kid, but still a real experience for Sam). What finally shuts Sam up is when Dean says this: "All right, don't have one of your episodes, okay?"
This gets Sam to stop complaining, and as far as we know, he never complains about PPMM again. When Dean apologizes later, of his own initiative, Sam downplays it: "You know what, man? Honestly... getting my ass kicked by those juggalos tonight was, uh... it was therapeutic."
A reference to Sam's mental health issues is all that it takes to end the complaints.
Let's go back seven episodes.
“And I woulda told you, eventually, once I knew that this whole ‘waving a gun at Satan’ thing was a one-time show. I think it's reasonable to want to know that you're off the friggin' high dive, Sam. You almost got us both killed, so you can be pissed all you want, but quit being a bitch.”
In The Girl Next Door, Dean is using Sam's mental health problems as an excuse to lie to Sam - a lie that began literally two episodes after Dean was furious with *Sam* for lying to *Dean*. And Dean was furious at Sam more because Sam was lying than because of the nature of the lie.
“I’m going to let your friend go—oh, wait I’m going to kill her” is not a minor lie. I have written at length about the rightness or wrongness of killing Amy, but at the very least I think it’s safe to say that killing Amy was a fairly new situation in terms of when to kill and not to kill, and Dean’s choice was completely contradictory with most if not all of their future choices. Including, you know, the witches two episodes later. So Dean’s claim that killing Amy was necessary makes no sense. “You couldn't do it, so I did. That's what family does -- the dirty work.” That doesn't ring true.
And as in The Mentalists, Sam and Dean are arguing. I have problems with the arguments on both sides, but they are talking. It is again worth noting what finally shuts Sam up, what Dean says that shames him into voicelessness: Dean bringing up Sam's mental health issues: “And I woulda told you, eventually, once I knew that this whole ‘waving a gun at Satan’ thing was a one-time show. I think it's reasonable to want to know that you're off the friggin' high dive, Sam. You almost got us both killed, so you can be pissed all you want, but quit being a bitch.”
Sam has no comeback.
Note how neatly Dean diffused blame. Much has been said about the “quit being a bitch”, but even I tend to forget the whole sentence. Dean blames Sam for something that wasn’t actually Sam’s fault at all, and tells Sam that because of that, Sam should “quit being a bitch.”
Some fans have pointed out that just because it wasn’t Sam’s fault didn’t mean that Dean didn’t have the horrific experience of having a loaded gun pointed at him by someone he loves. And of course, Dean’s initial response to the gun being in his face was to try to help Sam - and he succeeded at that beautifully.
But here's the thing: There were many times, in many ways, that Dean could have expressed his feelings about Sam pointing a gun at him. He chose to keep it to himself until he needed to get Sam to shut up about something Dean himself did wrong.
Let’s pretend, for a moment, that Sam WAS fully responsible for pulling a gun on Dean. We still have Dean basically deflecting Sam’s complaints by say, “Well, you did X”. It would be like if Sam in Metamorphosis said, “You lied about Dad’s last words, so quit being a bitch.” It sounds horrible, doesn't it? It's almost as if S7 Sam's mental illness makes him *less* worthy of respect in Dean's eyes, in the eyes of some parts of fandom, and in Sam's own eyes.
And in fact, Dean is shaming Sam for something that was not Sam fault. Let’s look at that quote again: “You almost got us both killed, so you can be pissed all you want, but quit being a bitch.” A few sentences earlier, he sounded like he was expressing concern for Sam. Frustrated concern, but concern nonetheless. But this sentence is clear: “You almost got us both killed”. That’s an accusation. It’s a nasty argument, responding to someone else’s objection to your behavior by shaming them for theirs. Oh, yeah - shaming them for something that wasn't even their fault. Why did Sam pull a gun at Dean? Because he was hallucinating Lucifer. Why was he hallucinating Lucifer? Because he was stuck in a box being tortured by the devil for a length of time too ridiculous to mention here. And why was he stuck in that box? Because he jumped in there to save the world.
Dean tells Sam to “be pissed”, but he spends the entire argument explaining why Sam was entirely wrong to be pissed at all. Dean gets angry at Sam originally for being all “just the facts”, but that was exactly what they agreed to. The only thing Sam is doing that Dean could object to is being pissed - because it's on his own terms, and not Dean's.
Back to that conversation in PPMM.
After Dean makes his comment about Sam’s “episodes”, Sam shuts up, and doesn't complain about being left at PPMM again. On its own, Dean’s comment wasn’t shaming. It even seems, at first glance, like an attempt to poke fun at Sam in an affectionate way - like that joke in Born Under a Bad Sign about having a “girl inside you”. An attempt to make Sam feel better about something that really sucks.
But seven episodes ago, Dean DID shame Sam for his “episodes”. Quite deliberately. When Dean brings it up in PPMM, he’s trying to shut Sam down. And it works. I don’t think Dean's PPMM intentions were anywhere near as nasty as his intentions in the Mentalists, I think it was just too easy a tool to resist. But he created the situation where it was very effective - and very damaging.