I'm fairly new to this game, and I am far from what I'd even consider below average, but I have had plenty of games with bottom fragging, thrash talking douchebags with not even the slightest grasp on teamwork and morale. Having played LoL for about 1 years, I'm used to extremely toxic people, and honestly I just pity them for their lack of logic and manners, and their inability to remain calm and positive. Such people will rarely improve, or at the very least, they will improve at a very slow pace, most likely getting carried. There's ofc. also elitist fucks, who believes just because they are superior at the game, that somehow makes them superior human beings, with every right to flame the shit out of their team for performing poorly. If I'm in a game with 2 or more friends, and we're teamed up with either of these types, we usually just kick them, and we're more than happy to take the loss, because in the end, that is much more fun than playing with tunnel-visioned scumbags.
