What you are suggesting is called "blacklisting." You may be interested to learn that in many states it is illegal behavior itself. See https://www.nolo.com/legal-encyclopedia/free-books/employee-....
> Nobody wants to hire people to do their jobs, and get employees running their part time political projects with their fellow colleagues in paid office time, on office issues.
Union organizing is not a "part time political project," it is a legally protected right. See https://www.nlrb.gov/rights-we-protect/whats-law/employees/i....