Seems like every round that's not premade with my buddies there is always that "one" guy. You know the one that feels compelled to say wtf every time someone makes a mistake, or repeatedly says "this Darius" to the enemy team. One who cries "feeder" and shouts for "surrender at 20." Granted sometimes I too feel like like someone who is doing poorly deserves these comments but 90% of the time its the jerk bag making them that's ruining the game for everyone. How does everyone else handle these situations when stuck with a mean spirited team mate?

Mute.

mute that mother****er, then report his ass if he really was a (unt

Completely ignore this person, mute, or if you see the personality of this person begin to be negative in queue try to dodge but that's a high risk because you lose ranked points when dodging. what i do when i get a player like that i try play safe, get a good farm, and IF you can engage the enemy and you know you can kill him without risk then this person will appreciate you... i think :P

I would also say mute.. but if you do they might actually want to tell you something important later on.
Like if someone is M.I.A. and you cant see him say it you might get screwed.

After the game is over ignore them and they wont show up in your queue anymore.

I find positiveness is the best response, actually. I was in a game with a bad troll and a person who was "new" to their character. Being nice to the other team opened up sportsmanly communication and the troll was silent the rest of the game.

Mute button /command does wonders, also just stick to playing with your friends. Every game will have it's whiners. I had a Lux calling me noob once when I was 9/1 Ashe and out CSed in bottom lane, just cause I originally went mid (before figuring out why AD goes bot.)

I usually say something like "dont even go there/start that". I try to get them to stop their negativity before it starts. I also mention that if we start fighting then we will be spending more time typing/yelling at eachother then actually playing and thus ensure the loss. Surprisingly this tactic actually works half the time. The other half the time they start raging at me lol. Best thing to do is stay positive and support your team. If the game is going downhill fast then so be it.. every match has a winner and a loser. Can't win them all so we might as well go down pleasently rather then argueing and raging. If its a normal game you can remind them they are not losing elo and the the difference in IP between losing and winning is really not that much..

It usually starts in the queue, if you have a guy who plays one role, dont argue, let him have it so your team can possibly win, who knows maybe this is the guys only role. If you forced him into something else, he will either troll or suck at it, and its really your fault.

I get alot of that people who have a score like 4/11/0 and you are 7/1/4 and then you die once and they start whining at you for making a mistake or something.

Worst one was when I was a jungler go up to a bush on bot and the enemy jungler is in there and I ended up dieing. The support started calling me for 'being a moron who pays no attention to where any one is.'
I then tell him it wouldn't happen if he had done his job as a support and warded, the idiot then says supports shouldn't buy wards that is the junglers job. O.o