Unions at work
Surely if your workers are part of a union formed of people in the same trade, it *is* work-related and Google have just shot themselves in the proverbial foot - "you can talk about anything to do with work except anything to do with Unions" certainly sounds like the sort of censorship those laws are supposed to prevent.
Now I see why American lawyers need to make so much money; psychoanalysis when they finally realise how twisted their legal system has become!