I don't think the cork board analogy really works here. This sounds like a person (ab)used their position and access to the backend of a security tool (Chrome extension or not) to broadcast a non-security related message.

I think we can generally agree that if they were on a team maintaining protocol buffers and they baked an unnecessary ignored message into the encoded stream (about whatever) there should be repercussions for lack of good judgement.

Generally speaking, I am for workers self-organizing if they feel it is appropriate. It's not clear to me that Spiers should have been fired for this seemingly minor offense.