Mr. Monk and the Astronaut - S4-E14
Factual error: During their examination of the crime scene, neither Monk, Stottlemyer, Sherona, Randy or anyone else in the room wear gloves or any kind of other protective clothing. They handle artefacts that could be critical to an investigation of the woman's death, including a cheque made out to her, and they hopelessly contaminate them by doing so.
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