Sure, then it's no longer third party dissent but counterparty dissent in hiring non union. Obviously competitors will emerge to varying success to employ these excluded persons.
I’d also like to point out that you needed to have this framed in the context of a union negotiating the same way as a company before you were ok with it. Why the visceral reaction to unions but none for companies?
If the company and employee have choice to choose union/non union I have no problem with it. The visceral reaction was to denial of employment by mutual consent.