^ She lied to his face (more than once), and Castle's been consistently shown to be somewhat overprotective. And I think people are missing the fact the Castle was shown to be in the wrong for tracking her like that.
Good episode overall, though I admit the details of the cases are becoming less and less interesting than the interplay between Castle, Beckett, Ryan, Esposito, and Montgomery. In this particular case, the political situation of the city was more interesting. Taking down a corrupt DA mostly offscreen is a pretty big plotpoint; are they going to go anywhere with this?