"Salt of the Earth" (1954)
It's still one of the most inspirational Labor movies of any era, and it really puts to shame the languid indifference and/or passive argumentation that passes for "opposition" today.
That it is set in New Mexico, based on a real strike at a real mine in 1951, is a bonus. The movie deals with racial, ethnic and gender discrimination quite openly and productively; labor exploitation of course is central. But what moves people still is the fact that the strikers take charge of their own fate, they are prepared to suffer, be gassed, jailed, starved out, run over by rogue cops, etc. in order to achieve their objectives -- which they do -- and they are supported by hundreds of thousands of workers all over the country and the world.
Of course the picture was made by blacklisted Hollywood types who ran afoul of the Red-baiting of the post WWII era. But their work stands tall, today as yesterday, and it should be seen now as a reminder -- as a forceful reminder -- of just what "struggle" means.
Also available in a somewhat better version at Internet Archive.
"The People, united, will never be divided..."