Earlier quoted context omitted.
> Of course there are many dimensions here. In some dimensions unions are "evil", in some they are "good". The question isn't whether unions are good or evil, it's whether they're actually a counter to a specific evil that companies might commit. Since that evil produces more money for the company, you need an example where a union did something to reduce a company's profit other than by trying to increase the union'…
Decreasing the company's profit doesn't necessarily equate to a union taking its "cut" (of the profits). Think reduced hours, more vacation, sick leave, less hazardous environment. Here the union is a check against a corporation's motive to sacrifice work environment for profit.
All of those things are the union (members) taking more of the profit.
"work environment" (as you're using it) isn't some abstract good that the unions are protecting. It's "what do I have to do for the money I make?"
Changing that balance one way is reducing the union members' take. Changing it the other way is increasing the union members' take, that is, trying to reduce a company's profit by increasing the union members' share of the revenue.
We're still waiting for "an example where a union did something to reduce a company's profit other than by trying to increase the union's cut."