NYPD Officer Craig Matthews complained about an illegal quota system for stops and arrests. As anyone familiar with NYPD culture could predict, he experienced retaliation from his superiors for doing so. When he sued, the NYPD hit him with an argument that's outrageous but very likely legally correct: it's your job to report misconduct, so the First Amendment doesn't prohibit us from retaliating against you for doing so.
The Association of Lawless Broomstick-Fetishist Brown-Person-Groping Can't-Shoot-Straight Thugs has a point. Because their employer is the government, public employees have limited First Amendment rights to be free of employer retaliation for their speech. But in in Garcetti v. Ceballos the Supreme Court said that right protects speech on matters of public concern unless the speech is part of a job duty:
We hold that when public employees make statements pursuant to their official duties, the employees are not speaking as citizens for First Amendment purposes, and the Constitution does not insulate their communications from employer discipline.
Thus in Garcetti the Court said a Deputy DA had no right to be free of retaliation for pointing out perjury in an arrest warrant application because doing so was his job. I explained how this doctrine works — and how courts have made an exception for professors at public colleges — in this post.
The result is that an entity like the NYPD can argue that its officers are required by their job to report unlawful activity by their superiors and fellow officers, and that therefore their act of reporting such misconduct enjoys no First Amendment protection.