Mr. Monk and the Voodoo Curse - S8-E7
Revealing mistake: In the scene where the desks in the office are re-arranged, you can see that all the computers are on but none of them connect to any power point. NB: You can vaguely see that one of the computers is supposedly on Youtube while another is on Google Maps.
Mr. Monk's Favorite Show - S8-E1
Revealing mistake: The car that explodes isn't sitting in a striped parking lot space. In fact, it's very obviously parked out in the middle of the lot's traffic lane, well away from any other vehicles, precisely because the special effects crew are about to blow it up.
Answer: The two men are trying to work out a secret deal between them without involving the union, which means the workers' interests aren't being represented and defeats the whole purpose of a union. The mayor would lose labor's support and Cusack's union troubles would just be starting.
Captain Defenestrator