Shaw wrote this, rather than saying it, in a Statement that was published with his one–act play The Shewing–Up of Blanco Posnet. The play itself may be short, but it's preceded by a Preface, which is followed by something called "The Rejected Statement". The Preface and the Statement together are something like three times as long as the play. In it, Shaw seems to be railing about the injustice of censorship as applied to his plays. I don't know any more detail; I couldn't bring myself to read the whole thing!
The Preface comes in 17 titled sections, and the Statement in 19. The quotation comes from one entitled The Limits to Toleration, which is the fourth section in the Statement. It contains about 750 words; this seems fairly typical, but some sections are two or three times as long.
If you want to see for yourself (I don't really recommend it), you can find it on Project Gutenberg.
© Haydn Thompson 2024