Dean knew that watching the show was sort of like getting a glimpse into what the future had in store for him and none of it was good. He was skipping over the entire portion of what he watched was murdering an innocent kid while he tried to bargain with Dean. Tried to explain he wasn't involved in any of this but Dean only saw red. He only saw that he was a part of the family that had killed Charlie and he knew that wasn't the kid's fault. Charlie was his brother's fault. It wasn't even Sam's fault.
Charlie got involved the moment she knew Dean was in trouble.
His brain short circuited for a moment. Not at the sight of pie or the fact that Liv spoke with conviction over the fact they needed to stop the endless cycle of self-sacrifice but at the affectionate kiss to his shoulder. It wasn't something he expected. While Liv broke eye-contact, Dean was sort of just staring a little dumbly at her before bringing himself back into the conversation. Because what she said made sense, more sense than what he was making out the situation to be which was one of: this would only end one way, which was Dean punching and/or killing his brother.
"I never said it was smart." He did know that hating or killing Sam over what hadn't happened yet in their lives, was indeed stupid. The anger that he was holding back in his eyes, softened down a bit. The idea that he was just going to lash out at Sam right now...seemed sort of stupid. It was stupid. Dean didn't feel pandered or placated, but rather being put down quick and easy like ripping off a band-aid on the Winchester cycle of 'I blame this person'.
"I got caught up in it." He stated softly, knowing it was more of an excuse to lean back on something that was easy to get angry at. The truth of the matter was, the Mark was beginning to gnaw on him. Like an itch that couldn't be scratched and just finding out what happened on the show set him over the edge. "She wouldn't...I'm pretty sure she'd call me a dumbass. Or something in weird geek speak that I have no way of understanding."
He thought about it for a brief moment. "I don't know...I didn't even talk to him about it." He didn't really plan this out well enough in his head, but he was more of a doer than the talk-it-out sort of thing to see where his brother even stood on the whole thing.