Question

Why did some people distrust unions

Answer 1

The topic is an endless circle of debate. Do they hate Unions or how Unions act? (many probably haven't given it enough thought). Most people who bash their very existence on any level probably haven't heard of Harry Bennett's "goon squads" at Ford in the '30's. Breaking down doors of workers homes and using tear gas & billy clubs on not just workers but their wives & kids too. Or the Triangle Shirtwaist Co. fire in 1911, where management chained the exit doors, and people worked in shocking filth. You might not like how they operate in practice, but remember there was an original reason for their coming into existence.
Collective Labor & Capital's power is a swinging pendulum. Given a free reign, Capital will work labor do death in filthy dangerous conditions. If Unions ran companies, the long term goals of sustainable profitability would suffer.
I have worked as a skilled tradesman in both Union & non-Union shops. I have also been a first line supervisor in both segments of the work world. No one escapes some element of blame. I liked the pay, benefits & safety of the Union environment, but hated the protectionism of tasks, (waiting for an "electrician" to come & unplug my machine so I could wait for a "millwright" to perform some small adjustment, and wait for the "electrician" again to plug it back in), and I was on piecework. Harboring totally unqualified slackers with "seniority" was another tough pill to swallow.
This all being said, it's bad management that gives rise to Unionism, and also allows it to run amok. When Capital attempts to treat it's workforce as a consumable just like it's raw materials, or is too lazy to hold the line on outrageous demands from the Brotherhood, (because it might interrupt production and hurt their quota bonus this quarter) for the long term good of all.