Why do they punish "toxic people" and not trolls

So i just got a ten game chat restriction for "flaming" a teamate who after 40 minutes literaly said you dont deserve to win your bad then proceeded to sit in fountain for another 5 minutes. When katarina finally left fountain she ran into the enemy team and just died. I got the chat restriction though for being obviously tilted and a little angry from having this troll i said wow quit being a %%%%. i know i shouldnt say that but im really getting punished for someone intentionally ruining my game and me getting tilted from it. i dont see how thats fair but i guess thats how riots working right now. Oh and as far as i can tell this player has no been punished for his/her actions at all.