Sentence:  “I don't mean all of your friends—only a small proportion—which, however, connects your circle with that deadly, idle, brainless bunch—the insolent chatterers at the <WSD>opera</WSD>, the gorged dowagers,nb..., the jewelled animals whose moral code is the code of the barnyard—!" 
Meaning of the word marked with <WSD> tags:  A building designed for the performance of such works; an opera house.