Pretty sure his actions were actually illegal.

https://www.nlrb.gov/about-nlrb/rights-we-protect/the-law/em...

> Supervisors and managers cannot spy on you (or make it appear that they are doing so), coercively question you, threaten you or bribe you regarding your union activity or the union activities of your co-workers. You can't be fired, disciplined, demoted, or penalized in any way for engaging in these activities.