A large part of the problem is the indirect nature of the communication. People are much more likely to be confrontational when not face-to-face with the other person. It's not inherent in the remoteness, but it's evolved in it. The "ancient" Compuserve chat rooms were not that unlike this forum, but were much more polite. I was in several on a variety of topics, and while there were issues, the frequency of hostile replies was far lower than today. Then, people were so happy to find others sharing their interest beyond the handful who lived near them (if any) that arguments were quickly dropped. I see too much "my way or the highway" now. Sad.
Other pinball forums have had issues, too. Tiltforums has had threads locked when they got too testy. And as others have mentioned, a small number of loud voices are a disproportionate part of the problem.
I've dropped out of many threads of interest when I saw them get out of hand. While I have more Covid data than most, the discussion was out of control there early on and I saw no point in getting into the crossfire between sides. Too much "defending MY position" and too little "what's the real scoop?"
I've largely dropped out of "Game X good or bad?" discussions, too. Yes, I have opinions, and I've played almost all pre-Stern games more than most other people here. But what games I like and why are only relevant to people who play games for the same reasons I do. Some people focus more on art, sound, theme, etc., and will never agree with me on which games they like best. That's fine, and I have no need to convince them that I'm somehow "right". That's part of the key to calming things down - - recognizing that more than one position can be "right," for different reasons. Maybe more people here should read the "favorite lesser-known movies" thread and see that beauty is in the eye of the beholder.