I don't buy this analogy. If there's one thing news reporting has demonstrated over the last few years, it's that Google is not lacking in actual digital equivalents of noticeboards where people can put up the equivalent of posters. This seems like she decided that wasn't aggressive enough and implemented the political equivalent of slipping adware into a browser extension instead.
Apparently Google was already doing this with other sites. Why is this one different? It wasn't like she put up something that was illegal or could increase Google's liability. It's one thing to say: "Hey we don't like that one, change it." It's another to fire someone when they engage in a protected activity.
If she had put it up and refused to take it down I could understand firing her. But this is suspect for sure.
Putting adware into a browser extension that is already just adware (pops up messages on sites the employer doesn't want you to visit) is not a security risk.
This person used their access as a developer to alter internal security tools to promote their own messaging. That shows a profound lack of judgement, and it's not surprising their access would be revoked.
