True, but if you are being a douchebag in such a way that it interferes with a police officer's conduct of their duty, then that effect is not protected. So prosecuting this person for what they said would be wrong. Prosecuting for interfering in a Police officer's discharge of their duty would be though.
Incidentally this is my take on the 'shouting Fire in a cinema' issue. Shouting whatever you like shouldn't be a crime, just as firing a gun isn't in itself a crime. Context matters. Deliberately causing a panic is a crime, as is killing a person with a bullet fired from your gun. Intentions matter and even unintentional but negligently caused effects matter.
Incidentally this is my take on the 'shouting Fire in a cinema' issue. Shouting whatever you like shouldn't be a crime, just as firing a gun isn't in itself a crime. Context matters. Deliberately causing a panic is a crime, as is killing a person with a bullet fired from your gun. Intentions matter and even unintentional but negligently caused effects matter.