I agree with your concluding statement, but I don't think that the goal of moderating discussions is to get people to stop thinking particular things or to make them "good people."
I don't think you can pile everyone into a handful of platforms and get good communication. There's too many opposing viewpoints, too much crossover, and too much intermingling.
Forums didn't have the same issue because they were often single/few topic websites and you could just aggressively remove everything off topic.
The goal is to encourage actual communication.