It’s been my observation that a company gets the union it deserves. A lot of unions conduct their business very peacefully and productively with employers.
I worked for an industrial company once. The line workers were unionized, but the office staff were not. One plant, the office workers voted to form a union. The rumor mill attributed the result to one asshole manager, who also ignored everything but favoritism in picking who got job postings. When you were a clerk or a secretary, you generally had nowhere to go but sideways. If the process of moving around seemed unfair, if you had no hope of getting out from under an offensive boss, the morale level of a group would nosedive. Favoritism is the quickest way to create strife.
A good union is more like an ombudsman, bringing employee concerns to the top bosses without getting a single person labelled “troublemaker”. It also irons out rules that are written and fair, so that when someone gripes (“why didn’t I get that assignment?”) the boss can point to the rules and say “these were agreed to by all of you through your union”.
If the ushers went on strike, the musicians, the actos, the stagehands would all refuse to cross the picketline. The union generally is there for the protection of all - otherwise, it’s like the employers are wolves and can pick off the employees one by one (“Thin edge of the wedge” principle). The process fails if the actors or musicians don’t back each other up.
This also goes back to another thread, should a job be something the boss can take away or change at a whim? “Today you don’t work, call me tomorow and I may have some work next week” You can’t plan a life if you don’t have a reliable income. You can’t do much without a steady reliable income, IIRC it’s the core of a good credit score. So a job may come or go, but not on a daily timescale.
The people most vulnerable to predatory employment practices are the most unskilled, the most replaceable. generally, there are more possible employees than positions. This is why we have minimum wages, labour standards about hiring and firing, etc.
Basically, a union is a way for the employees as a whole to negotiate with the employer, thus giving them a more balanced level of power. If an employer refuses to negotiate, that says something about the employer.
Places like McD’s and Walmart refuse to deal with unions if they don’t have to. IIRC McD’s got some stores unionized in Quebec, and not long after closed them down “for economic reasons”. This business is a license to print money, and they don’t want to have to share it with their (unskilled) employees. OTOH, both sides are capable of nastiness. I recall talking to a fellow whose teenage daughter, a Walmart employee, was getting the pressure from the union organizers to sign up. he listened in and mentioned they laid heavily on the guilt trip and were totally misleading too. There’s plenty of nastiness on both sides. Some of the union brass I’ve met were dedicated socialists, they had the attitude that the employers were nasty so therefore that gave them the right to be equally nasty back.