This is entirely not true when discussing the conditions of work: see the National Labor Relations Act. Nor is it strictly true for speech that takes place outside the workplace.

> This is entirely not true when discussing the conditions of work: see the National Labor Relations Act.

The NLRA is pretty much toothless nowadays.

https://jalopnik.com/the-tesla-firings-were-about-unionizing...

https://medium.com/@GoogleWalkout/google-fired-us-for-organi...

> Nor is it strictly true for speech that takes place outside the workplace.

You are nominally correct. However, if I am your employer and I want to fire you I can almost certainly come up with some legitimate reason to put on the record. Your only recourse will be to file a wrongful termination suit and try to prove that the real reason I fired you was something other than what I said it was. Good luck with that.

Also, if you're in an at-will state, I don't even have to come up with an excuse. If I want you gone, you're gone.