If you're talking about act three, scene four, Hamlet demands to his mother, Gertrude, why she asked for him as he goes on to curse her on marrying her brother-in-law, a man who pales in comparison to old king Hamlet, her first husband.
Frederick Douglass wished that the slaves should be kept ignorant so they do not rebel or overpower their masters. He also thought that if they were to do this it could cause chaos in the south and create a racial war.