Under the TG FAQ page;
(found here)

All players should hold a professional level of conduct at all time. Please keep your language in the forums and on the server at a professional and mature level. (ie: FOX Television Standards) Play as though you are an example for other players and set a good one. New players will often follow examples set by veteran players, good OR bad.

I'm guessing this is where Fox came into the topic of language etiquette.

Also found in the FAQ

Online Gaming (basic rules of conduct)

* No swearing;
* No abusive behaviour;
* No racist, sexist or homophobic behaviour;
* Respect for Tactical Gamer and other members must be maintained at all times;

There's room to have fun with people, cracking jokes and what not, provided it doesn't distract the people playing the game. Aside from that, I think it's pretty straightforward.

It really goes hand-in-hand with how you present yourself in-game (playing as a team, not team killing, not using glitches, etc), like the code of conduct that is bound to those of us who wear the |TG| tag. You treat others how you'd like to be treated, and respect the space of those who don't appreciate certain behaviour. Acting "mature" isn't just about shrugging off things that you find offensive, but being able to comprehend that some people don't appreciate a certain type of behavior, and having the conscience ability to put forth the effort to make those folks comfortable, by holding yourself back and not acting out, being loud, or obnoxious in any way.