Maybe it would have been easier if he'd been able to control his annoyance, but Castiel wasn't particularly good with patience. At the same time, Adam didn't back down, and he was so very much like Dean in the way.

Including all the dramatics and threatening to let Michael in (again).

Castiel sighed. "Adam, I'm trying to help you. It may not seem that way, but Michael is also very powerful. I'll do what I can, but I'll admit I can't promise much. But things will go more smoothly if you're willing to work with me."

How could he ever prove that he didn't mean Adam harm? Was that even possible, or would their interactions always have this bitter undertone to them? Maybe that was simply how it had to be, considering their history or lack thereof.