> I can't imagine why someone would want to openly advertise that they're so closed minded.

It's not being closed-minded. It's not wanting to get sea-lioned to death by obnoxious people.

[WARNING: seriously off-topic comment, I was triggered]

Here's what sea-lioned means to me:

I say something.

You accuse me of sea-lioning.

I have two choices: attempt to refute the sea-lioning, which becomes sea-lioning, or allowing your accusation to stand unchallenged, which appears to most people as a confirmation of some kind that I was sea-lioning.

It is a nuclear weapon launched at discussion. It isn't that it doesn't describe a phenomena that actually happens in the world. However, it is a response/accusation to which there is never any way to respond to that doesn't confirm the accusation, whether it was true or not.

It is also absolutely rooted in what appears to me to be a generational distinction: it seems that a bunch of younger people consider it to be a right to speak "in public" (i.e in any kind of online context where people who do not know you can read what you wrote) and expect to avoid a certain kind of response. Should that response arise? Various things will be said about the responder, including "sea-lioning".

My experience is that people who were online in the 80s and 90s find this expectation somewhere between humorous and ridiculous, and that people who went online somewhere after about 2005 do not.

Technologically, it seems to reflect a desire among many younger people for "private-public spaces". In the absence of any such actual systems really existing (at least from their POV), they believe they ought to be able to use very non-private public spaces (facebook, insta, and everything else under the rubric of "social media") as they wish to, rather than as the systems were designed. They are communicating with their friends and the fact that their conversations are visible is not significant. Thus, when a random stranger responds to their not-private-public remarks ... sea-lioning.

We used to have more systems that were sort-of-private-public spaces - mailing lists being the most obvious. I sympathize with a generation that clearly wants more of these sorts of spaces to communicate with friends, but I am not sympathetic to their insistence that corporate creations that are not just very-much-non-private-public spaces but also essentially revenue generators should work the way they want them to.