How to kill a troll: With kindness
So, it sounds stupid but hear it out: There's an old thing I've heard that I always loved which is killing someone with kindness. When someone is lashing out at you they normally want a reaction. If you react negatively then they will continue because it felt good, if you don't react then they will continue because they are getting annoyed, but if you react positively then you can actually get them to stop.
I'm not saying be passive aggressive, that's still a negative reaction. Simply be positive. Ignore their negativity, continue talking with your team and being positive. If your team isn't being positive then use /all chat (I'm sure if the game is going that bad you have some down time while dead) and joke around with the other team. Yea, they are the enemy! but it's just a damned game they just want to play and have fun too. It's being a good sport, because out of 10 people in the game I'm sure you can find at least 2 of them that are positive (you + 1).
I see a lot of toxicity in the game, but it's everywhere - here on the boards and what not too. Too many people that forget that people have feelings, or people that have been abused by someone else and in turn are passing on it again. The cycle of rage and anger needs to stop somewhere, I'm just hoping to start a seed for that.
And, if you yourself start to get angry at the game, don't take it out on your team or you're the one that people are complaining about. No, I don't care if others are doing it too that doesn't mean it's acceptable to do and no I don't care if they ARE feeding. Unless the person is intentionally running up and dying without trying to fight back or escape they are just playing badly and that could be for any reason. Remember that thing above? Stay positive and help them out. You CAN turn around a game when someone is doing poorly because one person or one lane doing poorly will not make the entire game a guaranteed loss.
Seriously, if each person adds a little positivity then we can raise the overall attitude. Have more fun, chat more and make jokes! It's a game for crying out loud!