"Well, I don't want the pie to be a horrible experience for you." He wanted to turn this towards her rather than turning into a discussion about his FEELS. Dean was hurting. His chest...hurt. The thought that he would go home just to walk in and see that someone he cared about was dead. Discarded in a bathtub because his brother decided to play with fire. Someone who wanted nothing to do with this at one point and it was all the Winchesters' fault that she kept on getting dragged back in.
He knew a part of him wanted to blame Sam. But he was mostly blaming himself. He knew what his brother's tendencies were. Save the other without regard to the clear and present dangers. He paused for a brief moment. "You think whipped brains would taste good? I mean for you? Does the brain have to be intact to be...a "good eat"?"
He chuckled a little, finding momentary comfort with Liv leaning against his shoulder. "It's...my friend, my...sister is going to get killed because Sam dragged her into the stupid project of getting the Mark off my arm. Even if I keep saying don't. He does it behind my back and she gets killed." Because of him. It all boiled down not to what Sam dragged her into but why she did it in the first place.