I'm of the mind that what you get out of chatting in a public game is directly correlated to what you put in. If you want to just throw a sweeping generalization of "everyone is a racist/homophone/asshole" out there then that's all you're going to get out of it, ever.
I made tons of friends over the years on XBL just randomly hopping into a game with a simple "Hey whats up" and getting a similar response. Playing and conversing and having a good time, then throwing out the friend request when the session ended.
Some of the best memories were in Gears of War where when you died, you'd be tossed into the "death chat" and you AND your opponents would have a chance to talk shit or just comment on what's happening in the game. So many great moments of actually spectating games with people and having a blast. I can remember adding opponents just based on the fact me and my friends would have great matches against them and agree to meet up and play again.
That's all gone with Party Chat. Now everyone just loads that up, invites their friends, then they go join a game. It's ingrained now in the online community that that is the routine and it's really killed my desire to ever play online anymore.