Sure, you can call the police ... just don't expect them to do anything. Even if this is somehow a crime in GA (maybe they have some statute covering online harassment or threats, I dunno), the odds of them seeking a search warrant for Facebook, ISPs, and maybe other entities in order to track this guy down is somewhere between zero and zilch. A stranger making a crude and crass comment on the internet is hardly the crime of the century. And if the police investigated every such incident, we'd have to shut down every other element of government to fund the investigative units necessary to conduct these investigations.
So, move on, stay off of forums and discussion groups where things get heated, and try not to engage yo-yos in debates.