SpaceX said to fire employees involved in letter rebuking Elon Musk
This is a very predictable consequence of criticizing your employer via a public letter. Criticize internally all you want, and influence the changes that you want to see happen. Employment is a two-way relationship. If you don't like your employer, you are free to leave. If they don't like you, they are free to fire you (within legal bounds). Publishing an openly critical letter and signing it is a quick way to get your employer to not like you.