Try to be the "Adult" in the Room when dealing with toxic players
Just had a game where my support decided to criticize me during a failed gank. Rather than explaining my view of things I simply fullmuted all ( in case any others decided to dog pile in) and focused on the game.
A short while later he started taking my cs. At this point I didn't give him any reaction, just did my best to get what I could. After a while, I said "Lets work together" and nothing else. I just let that suggestion hang, as I was unable to reply to any sarcastic responses since he was muted.
And it worked...he started playing to win. During the post game lobby I realized he shifted his trolling towards the enemy blitzcrank.