This case was actually one I reviewed earlier today. The behavior struck out to me as slight antagonistic, but it wasn't enough to punish; especially since there was only one match displayed. However, in cases like these I like to investigate a little deeper out. It's been my experience that only in rare cases do completely non-toxic players end up before me in the Tribunal.
When I dig deeper I like to look at things like your over all report history, some individual chat logs from the games you played, and some past tribunal cases you might have had.
What I found was that in times where you get frustrated you often turn into troll mode. In games that go perfectly, this is rarely a problem. You can be a teammate others want to play with. But there are many examples where when things don't go your way you seem to throw your hands up in the air and give up.
It could be because you didn't get what you wanted in champion select, or perhaps a player didn't do to well on your team. In some cases you might just have had a bad game.
Regardless, it's clear that you have a temper, and to avoid future suspensions you're going to have to find some ways to manage it in game.
I'm afraid the final nail was a few reports from other players to our Support staff. Contained within were very specific screenshots of your behavior in champion select demanding roles from other players, and your willingness to troll anyone who defied you.
Moving forward, you're going to have to work on an attitude change. Unfortunately sometimes LoL will be frustrating. We won't get what we want, and we won't be able to win every game we play. How we deal with these setbacks will determine whether or not we can really succeed in this kind of environment. You'll need to find more productive outlets for dealing with this kind of frustration.
Less harping on poorly performing players, and more importantly, if you join a game and are unhappy with the Champion selections, then it would be much better to simply quit out of the lobby yourself, rather than to try and force someone else to quit by trolling the match.