My grandfather and dad both worked factory jobs and were both “diehard anti-union”.
After asking a few questions I got the sense that they were both convinced of the evils of unions by the employers propaganda. They would show them videos and have occasional anti-organizing events were the company basically said “you organize and everyone will lose their jobs”.
One year I remember that organization was talked about by my dad around Christmas time. They shutdown the factory for a couple of weeks (to really hurt the workers during the holidays)and sent out letters saying that unions were responsible for the shutdown and this would only continue if they organized.
Another time when asking my grandpa about unions he told me that the owner of the factory took good care of employees and didn’t need a union. That his boss would throw a big Annual party with raffles and a $1000 grand prize. But if anyone ever thought about a union, all parties would be canceled and lots of people laid off. It was part of his speech almost every year.
Of course my blue collar immigrant family would be scared of unions, their employers basically held their jobs over their heads.