"One half of the world cannot understand the pleasures of the other."

While I cannot defend Emma, however sincerely she believes her ends justify her means, this little mention of Mr Knightely shows that what he says to her is at least, not unheeded.
I love the layers of meaning in this quote. Mr Woodhouse quarrels with the Mr Knightleys' rough treatment of the boys, Mr Knightley quarrels with Emma's rough treatment of Harriet (to which the subjects submit with delight). It echos the same universal sentiment of the French phrase "vive la différence", and reminds us that even while Emma is focused on the current attendance of her father and anticipating the future pleasures of her sisters visit; even while she objects to Mr Knightley's views and believes herself completely in the right, his words are not forgotten, and still nettle her.