First of all, let me address this:
...and I don't think its f air that I get banned even tho others were the ones who started it and were nasty to me.
It doesn't matter what the other players said or did, it does not excuse your own actions.
I get perma banned for standing up for myself.
Standing up for yourself, or retaliating?
When you have the option to completely squelch the other player's chat, there really isn't any good reason to stand up for yourself. Just mute them and you won't have to put up with their flame.
Beyond all that, I personally can't take your word for it that you didn't flame. If you think your punishment was unjust, you should send a ticket to Riot Support, but I'd also recommend posting the chatlogs associated with your punishment so that the community might be able to find what crossed the line, and whether or not you did actually flame.