Final answer:
Peter gets angry when his parents threaten to lock the nursery, a place he and Wendy have become deeply attached to. The nursery represents a virtual refuge from reality, and the idea of losing it is what leads to Peter's emotional outburst.
Step-by-step explanation:
The tension between Peter and Wendy arises from the control and use of the nursery in their technologically advanced home, as depicted in the scene where Peter gets upset about the nursery being locked. George and Lydia Hadley, the parents, decide to lock the nursery after realizing that their children, Peter and Wendy, are spending too much time in the African veldt simulation, which has started to become disturbingly real.
Peter's anger is a reaction to the threat of losing access to the nursery, which has become a vital part of his and Wendy's life. The situation escalates when the parents notice the children's abnormal attachment to the virtual world created by the nursery. The culmination of Peter's anger is demonstrated when he locks his parents out, showcasing his desire to maintain control over this virtual environment that has become a refuge from reality.