how did cyril and dory pearson justify their behaviour
Answers
They think they are more knowledgeable than their elders just because they have more freedom and more opportunities and access to gaining knowledge.
Answer:
Doris and Cyril were astonished at Mrs Pearson's changed behaviour, they could not believe their mother was talking back to them and standing up to their bullying and ordering. They were both shocked at their mother's sharp retorts and the casualness with which she treated them so much so that Doris burst into tears and Cyril was enraged.
The complete disrespect that they had for their mother comes out in their discussion of how it is going to be when their father comes home and finds her like this. They did not care to enquire into why she seemed changed, they just wanted to figure out how long it would last so that their mother could go back to being their personal servant.