For pilots who are actively operating an aircraft, like a helicopter pilot would be during a drop off or pick up operation, it can be helpful to inform the local law enforcement types that aircraft flight operations are regulated solely at the federal level, and that interfering with a flight crew is a serious federal crime, particularly if the person doing the interfering happens to be carrying a dangerous weapon when they are intimidating the flight crew.
Smart local law enforcement types when they realize that 49 USC ยง 46504 applies to them, and some FAA or DOJ guy may decide to be a jerk, usually calm down.