Ignoring everything that has been happening lately, NOONE can deny that the look on Sam’s face when he realises the crazy dude is going to cut Dean’s throat is sheer terror.
Just listen to these words again and again and again. Watch Sam’s expression closely. Whatever everyone thinks, Sam STILL cares. It’s stupid to actually think that he would be ok with Dean dying. He worries about him and he loves him. He’s just too hurt to fully show it. He keeps his distance.