Det. Loki's superior in Prisoners is also often slightly rude. He cancels the surveillance at one point, and does many other disturbances to the investigation. Why does he seem to damage Loki's investigation?
The main example I can think of is the one you mentioned about calling off the surveillance from Alex Jones. He does this because Alex Jones is no longer a suspect and as he mentions in the movie, they couldn't afford to be wasting department resources.
He's simply doing his job as superior to make sure their resources are used in an efficient and effective manner.
Loki's frustration about him calling off the surveillance is that Alex has disappeared during this time, and had Loki known the other car wasn't going to be there, he would have gone there himself and would know where Alex was.