[Even after having it spelled out for him, it doesn't make much more sense. Castiel glances over at Blake as they walk, trying to determine how someone like him could ever end up philandering with a demon.

And more than that, why would he pick Crowley over Dean? Because that's what it would be, a choice between the two.]

I can tell you firsthand that it's a bad idea. Relationship was never part of the equation, but I worked with Crowley for a time and it didn't end well.

[Which is as much his fault as it is Crowley's, if he's being honest with himself, but the point is that teaming up with a demon in any way is not recommended.]