What is it about the Bokanovsky twins that John abhors?

John finds Linda in an unconscious state and tries to rouse her. Meanwhile, the head nurse leads an entire Bokanovsky group (a large group of identical twins) into the room for their death conditioning. The boys act as if they are in a game room, and the head nurse encourages them to have fun. The idea is that if death and fun intermingle, then people will lose their natural fear of dying. When the boys notice Linda, they make fun of her ugliness and fatness. John angrily picks one of the boys up and tosses him away from her. The head nurse is upset that John interfered in the death conditioning and warns him to behave.