Even still, there are appropriate channels and using a public platform to personally attack someone is a nuclear option that you should expect consequences on.

e.g. government employees initially raise concerns on policy privately, then resign and speak out when the discussions fail.

Personal politics, and hopefully politics in general, have nothing to do with the policies that result.

That depends on if you are a platform or a publisher.

"I disagree with what this platform I'm working on allows," is a valid statement an employee can bring up and unavoidably political when in reference to political speech or something that is being used to some political end. A section of some arbitrary law from the 90's doesn't define what an employee can be concerned about.

That seems like a fine way to state your political stance on the platform. But as has been brought up in other comments and the article, it is not the manner in which the dismissed employee did it.