The Biggest Mistake Garrett Ever Made On Blue Bloods

At the end of the day, Garrett has one job, no matter how much Frank values his opinion and insight. As the Deputy Commissioner of Public Information, Moore focuses on the relationship between the NYPD and the public, namely the media. He attempts to steer Frank's comments and actions to represent the department in a positive light to the people. As he reminds people often, that is no easy task. However, his biggest mistake comes when he neglects his own rules and is caught acting in ways that negatively impact the department's image.

In Season 7, Episode 17, "Shadow of a Doubt," a reporter publishes an expose on DCPI Moore that implies the commissioner's number two accepts gifts from people, presumably in response to favors he gives out. Frank takes issue with this assertion and tells him that he must hold a press conference, committing to repaying any gifts he has been given out of pocket. Moore takes exception to this and gives the always potent response of "or what?" Frank later discovers Garrett is living in a hotel due to having marital problems, laying the groundwork that Frank doesn't know the DCPI as well as he thought.

Eventually, Moore gives the press conference, and all is forgiven. However, this is a mistake that simply makes little sense. Moore's entire job is to avoid this behavior and ensure others do as well. In fact, he spends most of his time on-screen advising the group to work opposite of their instincts, which rubs viewers the wrong way at times (per this thread). This moment projects the image that Moore is corrupt and has a price, someone who could easily be bought. This is more dangerous, knowing he has the ear of the most powerful lawman in the city.