Historically, this doctrine has been used to prosecute people who have abused police officers verbally. As with the fighting words doctrine as a whole, the status of the doctrine with regards to police officers is unclear.
The doctrine was first set out in 1942 when a man was arrested and convicted for calling a police officer a "fascist." (This is the Chaplinsky case in the link below.)
However, subsequent court cases have not tended to uphold the doctrine. For example, a man in New Orleans in 1972 was charged under a law that prohibited
opprobrious words or abusive language, tending to cause a breach of the peace
when he was abusive to a police officer. This conviction was struck down.
On the other hand, some recent lower court cases have implied that the doctrine is alive and well. (Follow the freedomforum.org link for details.) This makes it very difficult to know what the current state of the law would be with regard to fighting words directed at police officers.