We can metaphorically (but like, hopefully it's a good metaphor) think of speech as being the sum of a positive-sum information-conveying component and a zero-sum social-control/memetic-warfare component. Coalitions of agents that allow their members to convey information amongst themselves will tend to outcompete coalitions that don't, because it's better for the coalition to be able to use all of the information it has.

Therefore, if we want the human species to better approximate a coalition of agents who act in accordance with the game-theoretic Bayes-structure of the universe, we want social norms that reward or at least not-punish information-conveying speech (so that other members of the coalition can learn from it if it's useful to them, and otherwise ignore it).

It's tempting to think that we should want social norms that punish the social-control/memetic-warfare component of speech, thereby reducing internal conflict within the coalition and forcing people's speech to mostly consist of information. This might be a good idea if the rules for punishing the social-control/memetic-warfare component are very clear and specific (e.g., no personal insults during a discussion about something that's not the person you want to insult), but it's alarmingly easy to get this wrong: you think you can punish generalized hate speech without any negative consequences, but you probably won't notice when members of the coalition begin to slowly gerrymander the hate speech category boundary in the service of their own values. Whoops!