Out of curiosity do you notice this rampant negativity outside of the game threads? Is it as prevalent? You are fighting a crusade that thousands of message board posters have fought over the last 20 years trying to correct the behavior of those who lose rationality during the middle of a game they are emotionally attached to.
I’ve posted at dozens of sports boards over the last 20 years and I’ve seen this type of discussion in just about every one of them. I’m not saying you shouldn’t speak your mind, just saying you aren’t going to convince a bunch of people to not use a message board game thread as an emotional outlet.