in chapter 3, why does don quixote tell the farmer to stop beating his servant?

Specifically, Quixote is upset because they have blocked his entrance to the library. Quixote's niece, his housekeeper, the barber and the priest are discussing which books need to be burned when Quixote interrupts them. Quixote still believes that he is a knight-errant and he will not be convinced otherwise. Don Quixote assures the bewildered Sancho that some enchanter has transformed the faces of their opponents in order to gain mercy from his anger.Don Quixote has been brought back to his home in La Mancha, but he has not let go of his imaginations. His squire (after a fake nose fell off) looks exactly like Thomas Cecial, Sancho's neighbor.

The Knight of the Mirrors loses the battle and reveals under his visor the visage of the bachelor Samson Carrasco. The newcomer dresses himself in a glittering coat set with mirrors, the squires are roused, and the combatants mount and begin to fight. At this, the amiable conversation becomes a parley for a duel. The strange knight boasts of having conquered even the great Don Quixote de La Mancha, of having wrung from him a confession that no one excels the beauty of his mistress Casildea.

he does all the good he can to everybody a child may persuade him it is night at noonday, and he is so simple I can't help loving him.' After eating and drinking together and chatting amiably, the two squires fall asleep. The stranger says his knight is more of a knave than a fool, and Sancho says, 'Mine is not like yours then he has not one grain of knavery in him. The two squires compare the foolishness of their masters. Meanwhile, the two squires have retired to a separate place, where they can discuss their common interests. Desirous to learn more about Dulcinea's rival, Don Quixote begins to converse with the newcomer. The stranger sighs and laments about his mistress, Casildea de Vandalia. While Don Quixote and Sancho spend the night under some trees, another knight and another squire stop to rest in the same place.

In chapter 3, why does don quixote tell the farmer to stop beating his servant?