I was on a panel discussion of Henry James' 1880 novel Washington Square, and William Wyler's 1949 film adaptation, The Heiress. The panelists all hated Dr. Sloper. They thought he was horrible. They could not see why I liked him. They could not believe that, after a few weeks of class, Dr. Sloper was the first, and only, character from any of the works we had read, or watched that I liked. They did not see him clearly. I do. I see the man protecting his daughter, and maybe his money.
Catherine was plain. Let us just get that out there now. Catherine was not "the pick of the looks litter." Dr. Sloper knew this. Catherine was dull. He knew that too. Talent-less, not the brightest, not a good dancer, etc., etc., his sisters knew it; Catherine knew it; Morris certainly knew it. Why would one hate the man for being honest? While the other charatcters would not say what they really thought, he did. While Aunt Penniman told Catherine to run off with the man who loved her for her money, Dr. Sloper tried to save his daughter from making the biggest mistake of her life. He loved his daughter. If he had only cared about the money, he just would have cut her out of the will and let her go. He knew she would have been miserable with Morris. He saved her. Catherine rewarded this protection by turning her back on him while he was dying. Ungrateful is not the only word to use for Catherine, but it may be the best.
Hollywood does not want the viewer to like Dr. Sloper either. In the film The Heiress, the film makers decorate him as the uncaring man. He wears a pointy goatee fit for Lucifer. Film makers always have evil men wearing goatees like that. His wardrobe suggests he is just the stuffy doctor, overly formal and cold. The actor portrays him the way one may portray a plank of wood. He is devoid of emotion; he gives no hint of the inner turmoil that the man must be going through. Sir Ralph Richardson (the "actor" in question) took the easy way out and did not bother to get inside the real Dr. Sloper. He just went with the popular opinion.
The fact is that Morris (Montgomery Clift) loved Catherine's (Olivia de Havilland) money--simple. Find any evidence that he really loved her: I bet you cannot. The only person who really loved her, who loved her enough to hurt her, was her father. In the end he was right about everything; and everybody even his own daughter, hated him for it. Honesty should not be a reason to dislike someone, no matter how unromantic the truth may be.