Atwater Kent was a very prominent maker of radios in the 1920s — sort of the Michael Dell of his era. He told his factory workers that if they ever voted to unionize he’d shut the business down. They did. He did.
Having just sat through 3 days of practice for taking the PHR (Professional Human Resource) and having 1/2 of a day on Labor relations, I can tell you that to make the above statement today would get you in trouble. You can tell them that it is "possible" that the company would be closed, but you can't out and out state it. It's considered a "threat" to the process, and mercy on you if you piss off the NLRB (National Labor Relations Board) 'cause they will install a union in your business whether they employees voted for it or not, if the board thinks you are being difficult.
I loathe unions, but the stuff I learned about the board is scary. The Director of the NLRB is appointed by the President. And the country's president-elect is very pro-Labor.
Every HR manager in the seminar with me was very concerned about the next 4 years.