It really varies. I try to play like I play prisoner's dilemma, my first move is "courteous" and subsequent moves are to do whatever you do.

Sometimes you get teams of mature people who realize we're all in it to have fun, who will wait for you, crack jokes while you're all waiting, and generally make you feel better about the game. Those have been some of the best matches I've played, and included extending condolences to the other player when I've killed them and giving them tips on what they could do better after they respawn.

Other times, people will just yell at you, swear at you, call you names, constantly unpause the games, and just be horrible shits.

Also, I wonder what's different (culturally) about Russians, as they seem to be, by far, the less courteous of the bunch. I think they are racist towards Americans, so when someone speaks English, they basically go "fuck him, he's an American". A few of my friends go the opposite racism route, and say "fuck him, he's Russian", but I obviously try to tell them that you shouldn't be a dick to someone if he's not been a dick to you first.