OK, I’m sorry, but I’m going to have to strongly disagree with you here. Sam certainly has some blind spots when it comes to Dean (I won’t get into how these mostly relate to Dean’s treatment of him here), but expectation of physical (or otherwise) violence from Dean I don not think is one of them.
It is a complete and utter fanon fallocy to say that Dean doesn’t or wouldn’t ‘hurt’ Sam. We have seasons worth of evidence that Dean is more than willing and able to lash out physically (and verbally and emotionally) at Sam when he is angry or ‘frustrated’ with him usually when Sam has committed what Dean views as a transgression against him. The examples below are all without the Mark.
Here are two examples from S2 and S4 respectively:
S2: Bloodlust - Sam calls Dean on his lack of coping with their father’s death and pushes him on him trying to use Gordon as a ‘substitute’ for John. Dean’s reaction is to punch Sam, because he’s angry and to shut him up.
S4: Metamorphasis - Dean finds out about Sam using his powers to exorcise demons, which Dean is angry about, once again his reaction is to hit Sam, not once but twice. I’m including all five gifs here, including Sam’s reactions because I will discuss these later:
Ok, so there are a couple of important things to note about both of these instances and how they form part of a pattern in the way Dean hits Sam/Sam’s expectations with regards to being hit.
A very clear similarity in both scenes is that immediately before punching Sam, Dean turns away, as if he is going to walk off, therefore the attack comes on a Sam who is physically unprepared for the blow, this is pretty evident in the way that Sam’s head is snapped violently back in both scenes, Dean is hitting him at full force and Sam’s body is offering no resistance.
The next similarity is with regards to how Sam reacts immediately after being punched, I unfortunately don’t have the gif for Bloodlust, but as we can see here from the transcript, he says:
You hit me all you want. It won’t change anything.
In both Bloodlust and Metamorphosis, it is pretty clear that Sam, whilst perhaps physically unprepared for the onslaught is mentally and emotionally expectant of it. “You satisfied?” in particular, paints an image that this is a reaction Sam has come to expect of Dean when he is angry with him, that it is an established pattern than Dean takes out his anger on Sam in such situations and that Sam accepts this as the norm. It’s also worth noting that since Sam has an incredibly similar reaction in Bloodlust, which is the first time (on screen) that we see Dean punch Sam like this (although not the first time he has enacted physical violence of another kind), it is strongly suggestive that this is a pattern that stretches back to before Sam left of Stanford. Whether the punches at that point were given out by John or Dean we don’t know, but Sam clearly expects physical punishment for angering Dean in both of these scenes.
I think it’s also worth making an important point that, although Sam ‘accepts’ the hits in both cases, leading many to claim that he “can take it” - that even if we ignore the complete grossness of that as a statement, that Sam is, in fact, not without physical injury in both Bloodlust and Metamorphosis we see Sam physically recoil back and bring his hand to his bleeding face. To suggest that because Sam does not show obvious outward signs of physical or mental distress from the attacks means that he is immune to hurt from such is abuse apology and victim blaming at its finest.
Another instance of Dean dolling out punches when angry with Sam can be seen in The Girl Next Door:
I could not care less if the show tries to play this off as humorous, it’s not. Again Sam’s reaction to this punch is merely to reach for the nearest cold object to put against his eye, once again, Sam displays that he has been socialized into expecting and accepting this behavior as coming along with Dean being angry at him.
Although I guess we don’t know for absolute certain is Sam remembers this particular incident (but I’m pretty such he does possess all his memories as Soulless Sam), it should certainly demonstrate to us as a fandom, what a fallacy it is to say that Dean would never hurt Sam.
The brutal beating that Dean enacts on Sam in this episode involves him punching Sam no less than 18 times and into complete unconsciousness. Also worth making very, very clear that Dean had NO idea what was wrong at this point and that Sam had in fact just asked him for help.
Sometimes Dean doesn’t even have to be angry at Sam himself, in order to lash out with physical violence. At the end of Born Under a Bad Sign, we see Dean punch Sam because he was angry at MEG who had been possessing Sam. Dean literally uses Sam’s body as a punching bag for his frustrations with absolutely no ‘provocation’ from Sam himself, his body is being punished for another’s actions.
Lastly and not least, let’s just remember that Dean has punched Sam before with the Mark too, ostensibly with the aim of ‘protecting’ Sam, however I can personally say that mine and Dean’s mileage vary considerably in the interpretation of the word ‘protection’!
The only instances in which Sam seems even mildly surprised by Dean’s physical abuse are in ‘Born Under a Bad Sign’ and ‘Do You Believe in Miracles’ in both cases this is because they fall outside the normal transgression/punishment dynamic and are therefore harder for Sam to predict as possibilities.
All the above, strongly demonstrate that there is EVERY reason for Sam to believe that Dean might physically hurt him in the scene in question in Dark Dynasty, especially as it would fit into the expected and largely predictable pattern of transgression/punishment. In fact the scene bares strong similarities to that in Metamorphosis, wherein Sam was hit twice in a row, in terms of Sam being interrogated for having ‘lied’ or ‘kept something’ from Dean. And remember, Metamorphosis (and every single other example bar one) happened LONG before Dean acquired the MoC.
What I’ve covered above is just physical hurt that Sam might expect from Dean, this does not cover all the times Dean has lashed out verbally or with an emotional attack against Sam, which fall into an equally, if not more, frequent pattern, even if Sam didn’t think Dean might physically hurt him he had plenty of reasons to believe he might have done so in other ways.