It is surely true that unions corrected an injustice. Unfortunately, the unions became a source of power over the years that led to corruption of the unions as well. I don't really blame the individual workers, but rather the leaders ... who succumbed to the temptations of power and greed.
The American Auto business was formed in an era where capital was the ruling class and the capital-less were seen as industrial fodder not much above a slave. Unions were inevitable in that environment. Attitudes of this Dicksonian world die hard and slow.