Dean was pretty sure that Castiel was making one hell of a mistake, but it was the angel's choice to make. There were so few things, it seemed, that an angel could actively choose to do on his own, and this...well Dean couldn't tell him no. It didn't look like there was much time for negotiations, either, so he reached out, pulling Ruby to him.
He wasn't sure how all of this worked, but he knew that the demon shouldn't be anywhere near Castiel when he went from being an angel to being human. "Stay put." He hissed at her. "You getting destroyed in the middle of this won't help him one bit."