Eh, I agree with a lot but I think he missed a big point. He talked about us being self invested in the game and that is true, but the question is "how invested?" and I think that varies from game to game. I've said it before, but honestly people invest themselves more heavily in games that carry a label or goal that can be used to elevate their status as a person in their eyes. When they win, they feel great, but when they lose, they are losing more than a game and a bit of self investment. In League, if it's Ranked, they are losing MMR which means they are going to be playing with worse players and they are losing LP which means they are one step further away from their desired goal and what they perceive as their true label that they need to achieve in order to feel good about themselves. People that make such a big deal about Ranked are more emotionally invested in the game than others which is why they are the ones more prone to rage and when Riot also makes a big deal about Ranked, then they are justified in their behaviour of "I'm better than you because I'm Plat" and are even more likely to rage when they are losing a match. Telling themselves "it's just a game" doesn't work at that point because to them it does contain value outside of League -- it contains value towards who they are as a person.
Just a thought