@Riot Premade Trolling

So I just finished a game where I got flamed by a premade 4 man team in ranked. The Yasuo in the game literally said "I was going to feed when I didn't get adc" and ended the game as 1 and 11 and 0 assists. I asked for the jungler to help due to constant ganks from the enemy Ekko and Zed, and all I got was, you are bad, you are retarded. Our Xin Zhao ended up afk farming in the jungle all day, even when they are pushing down our tier two towers he was farming.. At this point I am very fed up and returned their flaming. I understand it is wrong to flame, but when your teammates purposely screw you over like that for the entire game, I can't help to control my temper. After the game of course their 4 man premade all reported me. And I just received a notification that I was banned for 14 days. So after I got trolled by 4 man, they reported me because I flamed them, and because they have 4 reports I get banned. To be honest I don't care if I get banned, but why not punish these guys who are purposely trolling people? I checked the Yasuo's game history on op.gg and he has so many games where he is 0 and 12, 0 and 11 and he plays with the same people every time. How are these people getting away with trolling? And how is it fair that only I get banned while this troll and his premade are off to ruin someone else's game? Riot, I know its not right for me to flame, I don't and won't argue with you on that, but when you get trolls that purposely ruin your game, why am I the one who has to pay the price?