If you think unions are the scourge of the working world, you will not be happy at “Pride,” which begins with the unmistakable sound of Pete Seeger singing “Solidarity Forever” and goes on from there. Ben Schnetzer, with the megaphone, is among the stars in “Pride.” His character gets the chain of unlikely events going. “Pride” stars, from left, Freddie Fox, Ben Schnetzer, Faye Marsay, Joseph Gilgun, Paddy Considine and George MacKay.