\Let me pose a hypothetical. A cop walks by your home, you lean out the window and call him or her a racist pig. Is that an arrestable offense?
I'd probably say yes. I'm almost 100% positive that nothing good will come out of someone yelling a racial slur out of a window at a uniformed police officer. If the officer deems you to be a "threat to society", he's going to arrest you. Anyone who yells racial slurs out their window at uniformed officer is probably a good candidate for someone who is "a threat to society".
If Dogfish (just picking a name out of the thread, not trying to state or imply anything) walks by your home, you lean out the window and call hima racist pig, is that an arrestable offense?
Probably not, as Dogfish is not a uniformed officer, but rather a civilian just walking down the street. But if Dogfish calls the police, and says that he felt "threatened" from the person yelling from the window, I'm 100% positive that they would show up and have a talk with the person in the house. Where it goes from there probably depends on what the accused person does or doesn't do. IE, mouth off to the cops and you are probably going to get arrested much like Gates did.
In reality, Dogfish would probably just bust a cap in yo ass, so I wouldn't be calling Dogfish Homey, or [censored] like dat! Wurd!