This is why I play ARAM 99% of the time now. It really doesn't matter what happens. Most of the time, people are at the very least civil.
You know, it's funny, I played a game with one of my friends just now - he made a custom game with me on one team, him on the other, and 4 bots each. We agreed to dominate the middle lane, and were able to do so mostly without interference from our bots. I played Jax and he played Varus. I'd never done anything quite like this before, and because the idea was for us to learn a few things (he's a far, far more experienced player than I am) we had some incredibly good times! First blood, for instance, resulted in me jump-attacking into the range of the turret he was hugging. We apparently both struck each other at the same time, and we both died simultaneously. There were some amazing saves with health potions, some barely-kills due to Ignite alone, and a couple of near kills where one of us survived with 10 or 20 health. No XP and no IP, but that was one of the best games I've played yet!
I also found out how ridiculous it can get if you buy multiple Warmog's Armors. o.o