Derek huffs at that, managing to glare even in this form. He gets up and shakes his fur out with a casual, unaffected air, like he hadn't just been basically cowering before him.

He circles Castiel and sniffs at him, getting used to his new scent. He butts his head against Castiel's hip and looks in the direction of his clothes, briefly considering shifting back and then whining again, settling back down on to the ground.

Being fully human means feeling human emotions at full force, and it's easier to take the coward's way out and dull them, push them to the back of an animal brain.