Speech is action and just as capable of breaking any rule or code as physical action. Free speech is also not really relevant here as it has to do with the government's inability to restrict speech.

I think it is certainly a very fine line to walk and people (including Google employees) will definitely see it in a lot of different ways. But, reading this as an outsider, the note appears to me to address the situation very directly and conveys a real sense of urgency (more so than I have ever seen from any of my employers, at least).