Without a doubt the worst community of any game is CoD. I think we can all agree on that. When I play (not often nowadays) I just mute everyone as soon as i join a lobby. That doesn't stop the frequent "hacker" "noob" "camper" etc etc PMs I get. Meh. It saddens me that this is how people choose to behave. The problem is that these idiots outnumber the mature people, so it seems to them that this is the normal way to behave.
Sorry but no. DotA/LoL/HoN takes the biscuit for in-game abuse and general community mean-spiritedness.