So heres my deal with this, regardless of how good riots report system is they cannot prevent this from happening. To think so is idiotic and you are looking through rose colored glasses trying to express your rage and justify yourself by blaming someone else. People can have off days that just one small thing can set them off. It happens to me although im often more quiet in game about it. Just because it bans some player doesnt mean every case can happen. Other times as i said before people are just having a bad day and decide to take it out on someone else.
Get off your high horse, realize you suck ( as every single person in this game, even those in challenger needs to), and continue playing. If you were meant to get out of bronze you will. If not you will stay there until you learn what you are doing wrong and need to improve upon.
Dont blame riot for the acts of people they cant control. They try their best, sure the report system could be better, but if you expect perfection you will always be dissapointed