I was the first non union employee of a union company.
The owner had bought out the Milwaukee office of Assist (data and electrical contractor), and opened his own business. Since Assist had been union, he stayed with the union in Milwaukee.
I was given the option, and chose not to. That set the trend for the Oshkosh office, which went entirely non-union.
Roughly a year later, we had a chance to work with the boys from Milwaukee. They kept calling us scabs, telling us about how we were getting screwed, how the boss was ripping us off. I finally asked their team lead (highest ranked guy out of their office) what his take home pay was: it was a bit shy of what mine was.
I was just an installation tech. He was in charge of all Milwaukee.
We had the same benefits, which the boss had set up without any arm twisting from the union. Point of fact, when we got insurance, we all got a raise to cover what insurance was gonna cost us.
The big difference was his union dues. So... what did those dues get him?
When the owner finally got tired of the lack of work and initiative out of the Milwaukee office, he shut it down. THEN, the union started making noise, threatening our other employees, and generally making a nuisance of itself. Which resulted in... nothing. And there was no help for the guys that had just lost their jobs: "Sorry you're unemployed now. If you get another job, make sure they're in the union!"
Seriously: most of the pro-union people I've met have come across as Jonestown types: don't confuse them with facts, they have their rhetoric, and that's all that matters!