I'm still not convinced this isn't a troll due to the shear frivolousness of it, and the graph by stalewee =p. But assuming you didn't grow up around early online gaming like many here did, I guess I can see how you would try to cut down on this more negative aspect of it.
But unfortunately, this is really a futile effort.
As soon as your son is given an internet connection he will be exposed to exponentially more flaming and bad manners than the supcom ai could ever muster. Though FA has less than the average, the mavnoobs, deathlys, cybrankillers, and iridiumBLOWS's will certainly find him. Don't worry, if he's older then 7 or so he's already heard it in school. I can distinctly remember saying whatever I wanted in elementary school but being very disciplined around my parents, and this was the prevailing behavior.
Also, "GG" is often used in a derogatory fashion. The winning side often drops an obnoxious preemptive GG, or players on the losing side say it when not in danger just to illustrate their disgust with their teammate(s). In FA I was exposed to the metaphorical/figurative GG - given by the losing player as if to acknowledge that their defeat is inevitable, though they intend to keep fighting and eventually bequeath yet another GG when they are actually leaving. Shep just gives the metaphorical GG at the beginning of our games. =)