If you valid reported him and he keeps up that kind of behavior then eventually he will get banned, The reason you got banned first is because you already had a history of negative behavior, and this game was just the one that was enough to warrant a punishment for you. Both intentional feeding and verbal harassment are equally bad and both do get punished as well. In fact, here's an example of a gameplay troll getting banned. Yes the example I listed is just one person that got punished but it does prove that people who troll via gameplay are indeed punished. As far as "mean" words are concerned, from the Tribunal FAQ:
What's the point of having a language filter if I can get banned for 'adult' language?
We aren't out to punish players who use adult language; in fact, very few players are ever banned for saying stuff like "f***, I missed that skill shot" or "damn, fing close game!" However, the language filter is not an excuse to verbally abuse someone in the game. When you verbally abuse or harass someone by calling them "fing *****" or "ngger noob", that's when you've crossed the line and will be punished by the Tribunal. I've said this before and I'll say it again, we aren't trying to clean online games of adult language; we're trying to reform or get rid of jerks who like to verbally abuse and harass other players.
Why is verbal abuse punishable if there is a mute button/language filter?
Players shouldn’t need to rely on features like the mute button or language filter to engage with other players in positive ways. When a player verbally abuses another player and forces him to use the mute button, they have already created a negative experience for that player.
If you must defend yourself then do so in either a neutral or positive manner. You're not defending yourself if you're retaliating negatively-you're just being a jerk instead. From Understanding the Tribunal:
4) That player in my game was far worse than me. Why am I banned???
a) I'll keep this one simple: retaliation isn't OK. Reacting to a toxic player by being toxic just incites that player to be even worse--it also ruins the game for up to 8 other players. It is far, far worse to watch two people yelling at each other all game than it is to watch 1 player ranting into blank space. Almost everyone in the game can find someone out there that behaves worse than they do--but so what? Finding someone worse doesn't justify your behavior or justify retaliation. We expect more out of our players. What players often don't realize is... those other players in your game that you thought were worse? Nearly 100% of the time, those players were banned even before you were. If someone is being toxic, just report them and move on. If you retaliate, both of you will be banned. It's really that simple.
P.S. comments like this:
Riot consists of a bunch of clueless wankers that are incapable of using reason or logic.
Are a very poor way of getting your point across there honestly, not to mention that they also give the impression that you're just looking to complain and whine rather than have a reasonable and civil discussion.