So what do you do when you get mad? I don't get it. Does your anger manifest in a way where you insult others for your shortfalls? I think counseling would be your best bet. We aren't psychologists. Or just mute all, but like you said, you get upset when you mess up, not specifically when people in chat upset you.
The best thing I could try to do is to open your eyes to how douchey it is to act that way. I'd probably get banned from the forums (again) if i really told you what I think about people like you that lash out at others because of their own mistakes. To put it as nice as possible, it's insecurity plus ego. Don't be an insecure little douchebag with a keyboard. Be comfortable with yourself and your own skill level. It's just a game. You don't have to be godly. It's funny being bad at a video game. Have fun with it. Idk.
I grew up stomping every one of my friends in video games. I was always the best and a bit of a natural. A friend could own a game, and I come over playing it for the first time and end up crushing him by the end of the day. So I had a bit of an ego coming into league of legends. (Also placed top 3 in several starcraft dream tournaments in my teen years). I quickly learned that I ain't shit. I can't even get out of silver, the second lowest tier of players in the game. So I don't get mad when I lose and fuck up anymore. I've fucked up enough to realize I'm just garbage at this game, and guess what? It doesn't affect my life AT ALL. It's a fucking game.