I worked at my employer for 32 years and my position unionized about year 25 of my career. Generally it was a respectful workplace, with managers and supervisors who did not to asshole moves like the above either before or after the union was form. But it was public sector, so pay was determined partly by the agency's management and ultimately by the state legislature. The immediate cause of unionization was the state granting no cost of living increase at all for 7 or 8 years in a row, in the mid 1990s when private sector pay in our immediate area was increase by 5 to 7% per year. So the union got us a pay increase, which more than paid for our union dues, and nothing else changed really. If there was a grievance the union would send a representative - but the union was not interested into defending an employee who'd done something indefensible, and our management was pretty good about not bringing employees up for disciplinary action without a very good reason. We got along very well for the most part.
I never felt the need to tell my boss to fuck off.