Also, for years there have been rumors of something called "The Cartel" which consists of Google, Apple, Microsoft, Intuit and possibly other companies. Basically if you had ever worked for one of The Cartel members you would never be hired by one of the others. Even if you left the first company on the best of terms you were effectively blacklisted. I'm convinced that not only does blacklisting happen but that there are various kinds and that it is a very widespread practice. I've known any number of guys whose careers have just died. Some of them ended up in the Arizona desert.
It is not enough to keep your mouth shut. If you want to keep your job you are expected in effect to bow before their false gods.