What does the writer mean when he says that for the young poet growing up in his family “the word white comes to be unconsciously a symbol of all virtues”?

The author is referring to the poet's desire to be “a poet—not a Negro poet." Hughes, on the other hand, asks black artists to express themselves and be proud of their culture, instead of imitating white artists and absorbing their culture. Hughes draws to attention the beauty of black culture, saying "Not 'white is right' but, as we would now say, 'Black is beautiful'".