Castiel is an Angel of the Lord. He is his Father's child, compatriot, warrior and watchman. He thanks his Father everyday for all of his blessings, for being allowed to sit at His table in Heaven.
Like a good son, Castiel loves his Father.
But as he tries to wake Dean from his thrashing, screaming sleep he thinks that maybe... maybe he also hates his Father just a little bit. He hates that Dean, an imperfect but righteous man, has been subjected to such horror and torture.
Dean is not the first, nor the only, to ever be subjected to such things; Castiel knows that. Over the millennia he has witnessed the suffering of millions of men, women and children, but he was always comforted by the fact that he knew those people would go on to their just rewards. The righteous go to Heaven. The wicked go to Hell.
Except Dean. Dean went to Hell.
Dean went to Hell not because he was wicked, not because he made a deal with a demon, but because he is righteous. Dean went to Hell because God, the Father, ordained it.
"STOP! NO! PLEASE STOP! OH, GOD, PLEASE STOOOOOOP!"
Dean screams and cries, and Castiel shakes him and grudgingly prays that the man wakes very soon. Suddenly Dean's eyes fly wide open and he scrambles as far away from Castiel's touch as he can get, convinced that the hands belong not to an Angel but a demon, Alastair, intent on ripping him apart.
Castiel waits patiently for Dean to calm down, to stop frantically darting his tear-filled eyes around the room, to stop looking for where the next blow is coming from. After a moment Dean's harsh pants become softer wheezes and his eyes draw into focus. "Oh God! Oh God, no!" He clutches the blanket tight in his fists and pulls his knees up to his chest. "No, no, no, no, no..."
Castiel scoots just a little closer, making sure that Dean sees him, making sure that Dean sees he is not there to hurt him. "Dean?"
"Oh God," Dean cries, tears falling freely down his face. "Oh God, Cas! Cas!"
Castiel pulls Dean into his arms, thankful that Dean trusts him enough to allow the comforting touch, thankful that Dean has his head down so he can't see the hardness and resentment in his eyes.
Castiel is an Angel of the Lord, his Father's child and a good son. But sometimes, when Dean is suffering, shaking and crying in his arms, when Dean looks at him with such pain and fear — well, then, sometimes Castiel truly hates his Father.