Castiel just looked at her, no compassion, no sympathy.
"You were wrong."
Again he let the silence stretch out, let the truth of what he said sink in.
"I know my brother. I know the way he operates. I was there, Ruby, at the rebellion, the war for the throne of God. I saw the way he corrupted his followers and I saw how he treated them afterward."
He shook his head once more, sitting down again, feeling every millenia he'd lived through weighing on his soul.
"He would have destroyed Sam. And his family. And me. And he'd have made you watch, laughing while he did it. He rewards no one. He betrays all. He was the Morningstar, the Lightbringer, but he became the Betrayer. There is nothing left of the brother that I once loved, so so much, left in him now."
His eyes gazed into the far distance, to beyond the dawn of humanity and to the days of war, when angel fought against angel.
"If he gets out, the mortal world will become like the Pit. Every man, woman and child will experience unimaginable torment as he takes his revenge against those our Father favors. It seems strange, talking about it in such a vague concept, so here's us making it personal," for the first time he met her eyes, black as they were, staring into them with an unflinching gaze.
"He would have torn off my wings, and placed me on the rack, and let every demon I've ever sent to hell have their fun with me. And Ben, you claim to care about Ben. A member of Sam's family. Think of everything Alastair ever did to you and now think of the being that taught Alastair doing that to Ben. That is what you tried to create Ruby. I hope you're proud."