This has been the story of my ranked solo games. I feel like in 90% of my ranked games this season. Someone starts flaming and the whole game devolves into a flame war and people are no longer focused on win conditions, the minimap, enemy's next play etc etc, they are just focused on typing.
Some games we are behind as fuck like last game 3 losing lanes and 0/2 jg. 2 drakes behind. No one says shit. We keep our head in the game. Play around win conditions and make sure we hold towers. Set up vision around neutral objectives and get some easy picks and win.
I feel like your team mates, even the "feeders", are often better than you give them credit for. But flaming them makes them go more mental boom and just play worse and worse. I went like 3-9 at the start of the season because I played with full fucking tilt.