It feels weird for me to read comments in this thread debating about and assuming a simple note about unionization or organization by an employee whose job it was to do exactly this kind of thing is "not in good faith" or a "violation". In my mind this kind of thing has the same sentiment as _any_ policy notice. The world in which notifying people that they have the right to organize is a "violation" is a really mess…
Performance does not matter: fire both the genius and the slacker for abuse. The factual content of the message does not matter: fire both those who lie, spam, or those who distribute relevant activist messages. Legally required company does not matter: if it is not your role, it is not your role (distributing these "facts" was never part of her job description, it has nothing to do with security. It is also naive to assume Googlers visiting that very website would be interested or unaware of this policy notice).
The controversy is because people have different opinions: those who feel activism trumps profession, and those who feel it don't. Like said, any company that employs security engineers who hold their activism as more important than their profession is a dangerous company worth avoiding. I am glad this firing happened.