Since the tragic deaths of his wife and infant son, Dr. Sloper has no one left in the world but his dowdy daughter Catherine. Truth be told, she's a crashing disappointment to him. Even so, he's not about to let her fall into the clutches of any gold-digger who might come along.
This explains his unwavering hostility to Morris Townsend, whom Dr. Sloper suspects of being a fortune-hunter. Catherine has fallen for Morris in a big way, but her father is convinced that he's only interested in her money and sets out to thwart Townsend's nefarious plan.
As well as disliking Townsend for being a gold-digger, Dr. Sloper also finds him to be something of a vulgarian, a man without good breeding or manners. In this snobbish, hyper-exclusive part of the world, that sort of thing counts for a lot. And it's patently obvious to the good doctor that Townsend just doesn't have what it takes to move effortlessly in this gilded milieu.
Despite Sloper's best efforts, however, the willful Catherine stands firm and refuses to break off her engagement. From now on, the relationship between father and daughter will be strained to the point where they will become estranged from each other, even after Townsend's no longer in the picture.