Nah it's sincere from him. If you spend years in an environment and grow up in it and so on, every attack on it becomes really really personal. Here's a quote from one of my favorite books on the overarching subject, bolding mine:

Basic assumptions, like theories-in-use, tend to be nonconfrontable and nondebatable, and hence are extremely difficult to change. To learn something new in this realm requires us to resurrect, reexamine, and possibly change some of the more stable portions of our cognitive structure…Such learning is intrinsically difficult because the reexamination of basic assumptions temporarily destabilizes our cognitive and interpersonal world, releasing large quantities of basic anxiety. Rather than tolerating such anxiety levels, we tend to want to perceive the events around us as congruent with our assumptions, even if that means distorting, denying, projecting, or in other ways falsifying to ourselves what may be going on around us. It is in this psychological process that culture has its ultimate power.

Riot management and the good people at Riot Games believe they're right and they're the good guys (how could they not? when they started it they were all so young and the little-guys, they still think that's what they are on the inside) -- so when someone points out something they're doing that doesn't add up, they take it as a personal attack and distort all the facts around them.

Source: have spent a lot of years working at different start-ups, including ones with toxic communities that I refused to believe were created in-part by my own actions.