"He would kill you."

Crowley pointed out without a second thought. Human versus the ultimate evil, human looses every time.

"And I do what I want most of the time but even demons have rules. You do have to appear to be following them."

Just give yourself a good cover story and do whatever you like! That was his motto. If it wasn't he wouldn't have an arrangement with an Angel. But one did have to be careful of spies.