The central idea of this passage is to tell the reader about good and bad examples of fatherhood.
Explanation:
The man with the child uses the "unfatherly expression, 'Well! give me peace in my day.'" Further down, it notes that a generous parent "should have said, 'If there must be trouble, let it be in my day, that my child may have peace;'".
the arguments are not considered universally true, therefore these elements are key. They show how an assertion can be strengthened through its limitations.
