This doesn't answer my question, and I didn't say anything about "freedom of expression" because it doesn't apply here.
Again, do you have a documented instance of an individual manager, preferably at a company larger than ~100 people, getting personally sued after a dismissal of one of their direct reports?
Claims of defamation are often part of discrimination and wrongful termination suits.
Nowadays there are forced arbitration clauses that prevent you from suing your employer in a regular court. Instead, you have to go to a private kangaroo court where they make their own rules, often not published in advance and that can change at any time for any reason.
Fraud, defamation (libel, slander), perjury, etc.
No matter what your position is, you are not free from the consequences of those.