Just look at your words and your words alone. It doesn't matter the reason, it just doesn't. Now, once you look at them do you see anything negative?
"so i called him a fucking trash scumbag for ruining my most important game"
That is negative, anyone can be punished for that no matter the reason why they said it. Please understand this, the reporting system isn't "Someone did something worse than I did so I should get a free pass."
"and told him "kys""
Telling someone to kill themselves over a game.
"i get perm banned for calling him what he is"
Is it really necessary to go out of your way and call someone trash, bad, and to kill themselves?
"_which resulted in me being angry towards everyone else in real life and with the anger building up I finally blew up _"
If you have these types of problems in real life over playing a game like this, you should have never been playing this game in the first place.
"This is why this game is cancer not because the game itself but the retarded system that perm bans you for talking shit in a VIDEO GAME." And many other big online multiplayer games, whether it be RPG or MOBA or any other genre does this too. You said people that ruin this game go unpunished, well you were one of the people that just ruined your game for your allies by saying those things and you got punished. You're living proof that Riot is banning the people that need it - even though they didn't ban the other person. There will always be trolls on the internet, but you just dealt with it the wrong way and ended up getting yourself banned. Riot has certain rules you must follow, and if you don't then you get punished.
THINK before you type
T - Is it True?
H - Is it Helpful?
I - Is it Inspiring?
N - Is it Necessary?
K - Is it Kind?