This little bit of truth is left out of the couple of professional adaptations and the 1941 Gabriel Pascal film of ‘Major Barbara’ available in the usual online sources. Having despaired of Youtube, Vimeo, and even Dailymotion, the answer was close to home. LA Theatre Works‘s 2007 adaptation, recorded live at the Skirball, keeps it and it flies. Upper class twit Stephen Undershaft (Hamish Linklater) attempts to lecture his plutocrat arms-maker father Andrew (Roger Rees) and gets dropkicked in the yodelay-he-hos for his troubles. Dakin Matthews‘s production is available at prx.org . Click on the image to open a new tab and listen at the site (the media player cannot be embedded here). Hop to 1 hr 06 min and 30 seconds by clicking within the wave pattern. Or, listen to the whole thing why not?
STEPHEN [springing up again] I am sorry, sir, that you force me to forget the respect due to you as my father. I am an Englishman; and I will not hear the Government of my country insulted. [He thrusts his hands in his pockets, and walks angrily across to the window].
UNDERSHAFT [with a touch of brutality] The government of your country! _I_ am the government of your country: I, and Lazarus.Do you suppose that you and half a dozen amateurs like you, sitting in a row in that foolish gabble shop, can govern Undershaft and Lazarus? No, my friend: you will do what pays US. You will make war when it suits us, and keep peace when it doesn’t. You will find out that trade requires certain measures when we have decided on those measures. When I want anything to keep my dividends up, you will discover that my want is a national need. When other people want something to keep my dividends down, you will call out the police and military. And in return you shall have the support and applause of my newspapers, and the delight of imagining that you are a great statesman. Government of your country! Be off with you, my boy, and play with your caucuses and leading articles and historic parties and great leaders and burning questions and the rest of your toys. _I_ am going back to my counting house to pay the piper and call the tune.
— Shaw, Major Barbara (Act III, Scene I)
(Minor update to the audio file timestamp on 5/25/22)