The WHOLE concept of "Online Rage" is a contagious mindset. People in online games do an admirable job of unlocking people's "Inner Asshole".
Your calm demeanor of "Win or lose, I just want to have fun!" is fine, but at the same time when you go online and some dickwad is teabagging you, belittling you, or losing and making up lies about them beating you and how trashy you are... It unlocks your Inner Asshole. When you see that guy online again, (unless you're Ghandi) you're going to be an asshole to that guy because of all the built up animosity.
Most players who play video games "competitively", do so for a lack of being competitive at anything else, like sports, or real life fighting. : To explain, have you ever seen how when someone Online has beef with you that isn't about player skill? Rather than resolving their differences maturely they usually revert to "Log Online right now so I can woop your ass!" The sad thing is they honestly consider their little controllable avatar to be an extension of themselves, as if smashing your avatar's unconscious body is symbolic in their fucked up minds that they're truly 'kicking your ass'.
People who play a lot of Online games all day pride themselves on their Video Game abilities, it's MORE than just a game to them. : How can you say to an Online player who has invested countless hours into getting good at a game that he sucks, and expect him NOT to get butt hurt? Games can be a huge time investment, and again, saying he sucks at a fighting game is like saying you could take him down and submit him Jiu Jitsu style and break his arm. You've just insulted his misplaced pride.
How have I dealt with Online Drama personally? : Well I've been around in fighting games for 5 years playing them Online and dealing with some of the biggest pieces of shit online has to offer, and lots of kind, friendly players. The thing is Online gaming used to be a huge part of my life because I was in school and didn't have a career, so when someone said I sucked at a game, I was determined to 'woop their ass' in that game. When I got good at games it wasn't because I wanted to get better, it's because I wanted to get better than OTHER people at the game. Big difference, and 90% of competitive players share that mentality.
The only cure is to not give a shit about commpetitive games enough to the fact that you don't give a shit enough about what Online people have to say about you. All the Online Drama stems from is people giving too many shits about nonsense anyways, like losing.