A Warsaw businessman came to the Chofetz Chaim with a list of seforim he wished to purchase from him. The Chofetz Chaim noticed that the man ordered all of the Chofetz Chaim’s seforim, except for the one on hilchos lashon harah. The businessman explained that in his line of work it would be impossible not to hear and speak lashon hara.
To which the Chofetz Chaim replied that he discussed this issue with R’ Yisroel Salanter and R’ Yisroel said it’s worthwhile to read the sefer on lashon hara if only to make the reader sigh when he learns it.