Using force and intimidation to coerce people into joining an organisation that gets to take part of their income, and dictate the terms of their employment is for their own benefit? How exactly is this any different from the classic protection racket? I'm not sure the people who were unemployed before a strike, and then still unemployed after it are going to buy into how beneficial this is for them. Nor am I convinced that the people who were happy with their working conditions, and were forced to take unpaid leave by the union that they did not join are going to see it that way either.
A lot of the tyranny that we have seen through our history on this planet has started off with somebody deciding that they know what's good for others better than they do for themselves, so they'd just be better off if you could make their decisions for them. The truth is that you don't get to make those decisions for other people, regardless of how important their compliance is to your own plans.