WaPo: https://www.washingtonpost.com/technology/2021/03/25/tesla-n... says Tesla:

* interrogated workers over suspected unionization efforts

* threatened workers with the loss of their stock options if they unionized

* fired one worker and disciplined another over protected union-related activity

* had a policy prohibiting employees from communicating with the media, in violation of their right to speak “concerning labor disputes and terms and conditions of employment”

Elon's tweet is a side-show.