Castiel looked up calmly, nowhere close to intimidated by Sam's height.
"You're being selfish," he told Sam quietly, his entire demeanor completely controlled. "Here, in your mortal world, terminal patients are allowed to refuse further treatment from their doctors. Many people have orders which force hospitals to let them die if that is God's will. I believe you call them DNR orders. This is no different."
At no point did he raise his voice, or tense his body, even a fraction.
"Margareta is not a simple person, no matter what you might think. She's a rational and intelligent woman who has made an informed choice, as is her right. I will not violate her trust."
Was he being cold? Castiel suspected Sam didn't even know him well enough to judge.
"Look at her, Sam. She asked you to leave and now you're trying to force your will on her. She can't even speak right now. Do you know what she's doing right now?" He looked over to Margareta, breaking eye contact with Sam for the first time. "She's praying. We should leave her in peace."