Why did the speaker made this statement to ato, ato to do not talk with the foolishness of your generation?

They then automatically assume that Eulalie is white and Esi (Ato's mother) exclaims: 'Why should my own go and marry a white woman?'. Ato then informs them that 'my wife is as black as we all are', and 'sighs of relaxation' fill the stage. That is before Nana overreacts and deducts 'And so, my grand-child, all you want to tell us is that your wife is a slave?', and when Ato attempts to correct her she dismisses him - 'do not talk with the foolishness of your generation'.