The Subject Which Must Not Be Discussed ? Is that still a thing? (infohazard related to Super AIs?)

I can see two other reasons. The first is that a culture WILL develop, and if outsiders see the political culture, we might not get a chance to teach them enough rationality for them to not be mindkilled instantly.

The second is that it's well established that smart people often believe wierd and/or untrue things. This, combined with the lack of respect for political correctness (in both the old-timey 'within the realm of policy you can actually talk about' and in the modern offensive language sense) and contrarianism, and a cultural site, could result in really bad politics.