I am here to source the quote and give credit to the translator, who did a really lovely job, imo.
This screenshot is from a play, as it happens. Brecht on Brecht: An Improvisation by George Tabori. (Here is a link to the 1967 Samuel French publication on archive.org.) Tabori, originally from Budapest (see wiki), translated a lot of Brecht into English and taught him in the US for a spell.
From what I can glean, this is his own translation. And indeed, it is an abridged excerpt from an (incomplete?) work by Brecht called Der Messingkauf. I came across another English translation of this and I do have a strong preference for Tabori's take.
Der Messingkauf itself is a little more opaque to me given the dearth of info I found via my internet searches, but much or all of it is in dialogue form. One website describes it thus: "Explizit wird diese dialogische Struktur im Messingkauf (GBA 22, 695 – 869), der zentralen Schrift der Brechtschen Theaterästhetik, die er ab 1939 im Exil verfasste und bis kurz vor seinem Tod weiterentwickelte und ergänzte. In vier Nächten sitzen ein Philosoph, ein Dramaturg, ein Schauspieler und eine Schauspielerin zusammen und diskutieren über das Theatermachen und seine Wirkung auf die Zuschauenden." Briefly, this is a text that Brecht worked on for many years, starting in his exile [from Nazi Germany] and returned to shortly before his death. In the piece a philosopher, a dramaturge, an actor, and an actress discuss the craft of theatre, etc. The passage celebrated by this post is spoken by the dramaturge.
Here is another archive.org link I found that contains the original German (should take you right to the passage once you log in and borrow the book). Tabori certainly gives a more poetic bent to the first line, "Man besetzt die Rollen falsch und gedankenlos (People cast plays wrong. And thoughtlessly.)." However, Brecht was himself a poet and Tabori is faithful with the anaphora of the next few lines, "als ob, als ob, als ob (as if, as if, as if)," and of course the line that so many are connecting with - "Too noble? Go look at the fishwives." - is an excellent rendering of the emphatic bent of the German: "Man sehe sich die Fischweiber an!"
Anyway, I love seeing Brecht around here because I enjoy and have learned a lot from the works of his I've read and/or performed. But I would love it more if people gave him and his translators due credit. Though I acknowledge this post sent me on a research jag I'm grateful for, since I now have Tabori's play to read.
I'll leave you with a quote from Tabori in his introduction to Brecht on Brecht, where he says:
The theatre is traditionally the healing art, our oldest priest and clown. Personally, I have found that Brecht is very good for what ails you, and should be taken, in large doses, against timidity, despair, confusion, and the worst of them all, stupidity. The cure need not be solemn or dull.