How are George and Lydia shown to have failed their children in "The Veldt" by Ray Bradbury?

George Hadley bought an expensive Happylife Home that is fully automated, to the point where his wife feels the house is raising her children more than she is. The feature that concerns them most is the nursery, because it is telepathic in addition to being automated. 

The children can control the nursery, and the parents do not like what they see. The nursery has dangerous animals from Africa. George also finds his old wallet in...

George Hadley bought an expensive Happylife Home that is fully automated, to the point where his wife feels the house is raising her children more than she is. The feature that concerns them most is the nursery, because it is telepathic in addition to being automated. 

The children can control the nursery, and the parents do not like what they see. The nursery has dangerous animals from Africa. George also finds his old wallet in there, covered with lion drool, and doesn’t know how it got there. 

"I don't know anything," he said, "except that I'm beginning to be sorry we bought that room for the children. If children are neurotic at all, a room like that—"

"It's supposed to help them work off their neuroses in a healthful way." 

George isn’t convinced. He brings in a psychologist to evaluate his children, who tells him the children are seriously damaged and he should tear the room down and bring them in every day for treatment. This surprises George, who just thought his children were spoiled. 

"I'm afraid so. One of the original uses of these nurseries was so that we could study the patterns left on the walls by the child's mind, study at our leisure, and help the child. In this case, however, the room has become a channel toward destructive thoughts, instead of a release away from them." 

By the time George brings in the psychologist, it is really too late. His children are sociopaths and he never realized it. He has only supported their behavior with his indulgence of them with this room. Automated houses and nurseries do not replace real human contact. The real way George and Lydia let down their children was not being there for them earlier, allowing the house to do it instead.