Other entities he owns are unionized - For example, WaPo is unionized:
https://postguild.org/about-us/
About the Guild
The Washington Post Newspaper Guild has been a voice for employees at the company since 1934. We represent 1,000 people across the newsroom and in our commercial operations including award-winning journalists and the talented marketing, advertising and printing plant staff who help readers and watchers find their work.
Every two years, The Post Guild forms a bargaining committee that sits at the table with Washington Post management to negotiate a fair contract for employees. This is The Post Guilds most critical job. In the off-season, our core leadership works with other members on a variety of committees to ensure Post employees feel empowered and that their needs are met and voices are heard.
Were proud to work at The Washington Post, a news organization that leads the industry in with its impactful journalism. The Post Guild is working to ensure that the company also sets the example for how newsrooms should treat their journalists.
Not allowing his Amazon employees to unionize (and calling the NRLB "unconstitutional"0 shows how deep his scabbery runs...