Unfortunately, there's no way to completely asshole-proof a game. When you play with randoms, you have to deal with the fact that a lot of them are idiots, or assholes, or in it for themselves. There's really no way to fix these gametypes, to compensate for human nature. That's why I absolutely refuse to play any sort of FFA or multi-team objectives games in matchmaking, and why I refuse to play Halo alone. After the nightmare that was trying to get to a rank 45 in Lone Wolves in Halo 3, dealing with people who'd forfeit victory just to pad their K/D ratio, who'd ignore the objective and go out of their way to hunt you down, I swore off anything that wasn't team-based, and I even got to where I didn't bother getting online unless I had someone else on my friends list to play with. Games like Oddball or KotH just don't work for FFA, and there's no way to fix that. At least with team objectives you have your teammates to back you up, but the only to guarantee they'll actually do that is if they're your friends. The only way to avoid or reduce your chances of getting matched with idiots is to avoid FFA and only go into matchmaking with a party of your friends.