The fact that they have it on this blatant of a propaganda poster means that unions work.
And going through union for what you need is much more effective and quicker than letting a supervisor/manager drag their feet and kick the ball around, and that's what makes union dues worth it.
The fact that they have it on this blatant of a propaganda poster means that unions work.
Not necessarily.
A poster this blatant means unions are bad for management.
It doesn't prove that unions aren't bad for both workers and management alike. Business isn't a zero sum game. To show that something helps workers, you need to demonstrate that it helps workers.
Which is to say, this poster is a bad argument for unions. The success of the writers strike, on the other hand, is a good argument of how unions protect workers from the bad deals management offers.