I played CoD4, Halo 3, CoD3, Gears of War, and other games on my Xbox 360 and only ran into an asshole about once every 10 matches. The problem isn't that big.
Now I play on PC, and it seems there's more of a scale. You get Minecraft, with hardly any assholes except the griefers. In fact, many people will go around giving things out for free just to help new players. Then you go down a bit to Bad Company 2. People don't even talk in that game. Next comes Black Ops. People will sometimes say NOOB, but that's about it. But more than Bad Company 2. And then there's Counterstrike: Source, where every second person is a screaming lunatic high on pot.
Oh, and there's also Team Fortress 2 which takes the two extremes and puts them together. You can't be in the middle if you play that game.