I can't speculate that for you. Try reaching out to them if you must know.

When we say open X, we expect something like the Via Negativa principle; instead of inviting members into a closed community, exclude those that violate the code of the open community.

This is false. Any "open" event (or anything, really) can be closed for select individuals.

The reason for this exclusion just can't be a banned criteria such as race.

(I.e. kicking someone out after they've stirred up controversy)

I'm not saying that this happened to you, I'm just addressing the point you made, that anything "open" can't or shouldn't be exclusionary.

Don't do that; use your AI, ask Claude for example